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CCNP Enterprise ENSLD (300-420): BGP Address Families and Attributes
3. BGP Route Selection
BGP route selection criteria Take the weight parameter into consideration first. If a router has two Otto paths to the same destination and their weight values are different, BGP chooses the route with the highest value as the best only when the two alternatives have equal weight. The next criteria for local preference is the route selection, which is influenced by these preferences. Prefer the highest weight. Prefer routes that the router originally preferred. For IBD paths, prefer lowest-medium external EBGP paths over internal; prefer paths via the closest internal gateway protocol. Most stable paths prefer paths from routers with the lower BGP router ID and the lowest neighbour IP address. A local preference value is preferred over a low value.
When the two alternatives have the same local preference value, then the next criterion is checked. BGP Weight Attribute The weight attribute is local to a single router; VGP never propagates the weight value, and this value constitutes a routing policy that is local to the route. There are two different methods for assigning the weight attribute to a route, with the higher weight being the preferred route. BGP routing polling can be specified using the weights "local routing policy" and "wide routing policy." BGP weights are specified by neighbouring default weight complex criteria. With root maps, the weight attribute can be assigned to a route in one of the following ways: Assign a default weight value to all the roots that are received from a specific neighbor. This weight value indicates that the neighbour is preferred over the other neighbors. Apply a root map based on routes from a neighbour to select some routes and assign weight values to them. Remember that a root map also acts as a filter.
Drop the roots that the rootmap does not allow in any statement silently. If configured, the default weight assignment on routes that are received from a neighbour is applied first. All routes that are received from the neighbour are assigned a weight value as defined. Default Weight When a root map is applied, it is configured on the router. The root map can be arbitrarily complex and give various selection criteria, such as a network number or a S path. To select routes, you can alter some attributes of the selected roots. The root map can set the weight values of permitted root selections in several route map states, giving the opportunity to assign a certain weight value to some roots and another weight value to others. A root map can also filter out routes if you want the routing policy to be exchanged among all the routers. In the AS, assign the Locherrence attribute to a root. On all internal BGP sessions, this attribute is carried with the rootroute. In this situation, all English-speaking routers within the AAS receive the same information. Normally, a router assigns a local preference to a route that is received on an external BGP session before it is accepted and entered in the BGP table of the border route.
Routers propagate the localpreference attribute on internal BGP sessions only. This policy constitutes a routing key for the entire BGP local preference attribute. Local preference is similar to weight. Because it is an attribute, you can set it once and then view it on neighbouring routers without having to reset it. This attribute has a default value of 100, which the router will apply to.Locally originated routes and updates received from external neighbours have the local preference attribute already. You can use local preference to ensure the A-S route selection policy. When processing incoming route updates, doing revisions, or sending outgoing route updates, any BGP router can set local preference. Except for EBGP updates with confederation peers, local preference is used to select routes with equal weight local preference in outgoing EBGP updates. Weights that are configured or override local preference settings to ensure consistent and wide route selection Change the local preference in the A. Also, do not use BGP weights. Local preference is the second strongest criterion in the route selection process.
If there are two or more paths available for the same network, a router will first compare weight. If the weights are equal, the router will then compare the local preference attributes. The prep path will be the one with the highest localpreference value. The local preference attribute is automatically stripped out of outgoing updates to BGP sessions. This practise means that you can use this attribute only within a single As to influence the root selection process. Local preference as the strongest BGP root selection parameter Remember the BGP root selection rules: highest preference and highest weight. Because you can use both weight and local preference to manage the route selection process, you must decide which one to use. If local preference is used, it should be the same foods. You can use weight on an individual router to override the local preference settings that are used and the rest of the A.
It is enough to change the default local preference on updates that come from external neighbors. You should avoid changing the localpreference attribute on internal sessions to prevent unnecessary complexity and unpredictable behavior. UI local preference in the following ways. Use a root map with the set local preference command. You can use the root map on updates from all neighbours or on outgoing updates to internal neighbors. This latter action is not recommended. Use the BGP default local preference command to change the default local preference value that is applied to all updates that come from external sources or that originate locally. BGPS path attribute, you can manipulate AS paths by adding S numbers to existing AS paths. Normally, you take the A or S path over the undesirable return path based on the incoming EBPs.
The S path that is sent out over the undesirable link becomes longer than the A path that is sent out over the preferred path. So the undesirable link is now less likely to be used as the return path. Modifying the AS path attribute is another method that BGP can use to influence the choice of paths in another autonomous system. For example, in this figure, router A advertises its own network at 170 and 217, one two.Its BGP is in autonomous system 65 and 538, and when the routing information is propagated to autonomous systems 65 and 45, the routers in autonomous system 65 and 545 have network reachable information about network 170 and 217 from two different routes. The first route is from autonomous system 65 538, with an AS path consisting of 65 500 and 836. The second route is through autonomous system 65547, with an AS path of 65500 and 476-555-0655 hundred and 36. If all other B GP attribute values are the same for all routers, autonomous system 65 545 would choose the route through autonomous system 65 538 for traffic destined for network 170 217 10 because it is the SHAWT in terms of autonomous systems traversed.
Autonomous systems 65 536 now receive Afric from autonomous systems 65 545 for the 170 217 network through router B in autonomous systems 65 538. If, however, the link between 65 538 and autonomous system 65 506 is really slow and congested, the set aspathprepend command can be used at router A to influence inbound selection for the one7217-10 network by making the route through autonomous system 6538 appear to be longer than the path through autonomous system 65 550. A S path prepending is known as manual manipulation of the A S path length. The A S path should be extended with multiple copies of the A S number of the sender. A S path prepending is used for the following actions, and to show that the properties selection will distribute the return traffic load for multihome customers, the length of the A S path is extended. Extra copies of the A S number of the sender are prepended to be added to the beginning of the A S path attribute to comply with BGP loop prevention and mechanisms; you should prepend no other A S number except that of the sender's A S path attribute. If you prepend another AS number in the AS path, the routers in the same AS as that prepended will reject the update. Because of BGP loop prevention mechanisms, you can configure prepending on a router for opening updates that you send to a neighbour or only on a subset of them as path prepending. Example administrative: one may prefer that the low-speed link be used for backup purposes only.
As long as the high-speed link bit is available, all traffic should flow toward AS 1 on the high-speed link, resulting in traffic flowing over the desired return path. To achieve this goal, configure the router in ASN-1 with Zbgp updates to ASN-200 to avoid having two copies of ASN-1. The S path A 100 has two options for reaching the network 24: the update that it received directly from the A s one and has a manipulated A s path length of three, or the update that it received from the YS 100 and was not manually manipulated and thus has an A s path length of two. When a S 200 starts the selection process for the best route to reach 10:00:24, it checks the Alength after the weight and local preference parameters. In this case, neither the weight nor the local preference have been configured. The length of the A-S path will be the deciding factor in the route selection process.
A S 200 prefers the short A S path and thus forwards packets toward 10 00:24 via A S 100. Ziad's administrative policy has been met, and A Sone will receive incoming traffic over the high-speed link. If the forwarding path from ASN 200 via ASN 100 to ASN 1 and ten dot O dot is broken, the BGP update to reach ten dot O 24 is revoked. In the event of such a nephilia, A S 200 will only have one remaining path to ten 00:24. The selection process now has only one choice: the route directly to Alaska over the low-speed Wan link. The low-speed link will therefore serve as a backup for the high-speed van link. Prepend the AS path with the AS number, not the AS number of the receiver. When you manually manipulate the A S path, the only valid A S number can be prepended as the A S number of the sender. Prepending any other AS number will cause problems. In the example S 1200, the Egress router performs "S path prepending" when the route is on its way to being transmitted to S 200. After the manual manipulation, BGP automatically changes the A-S pathing to the BGP specifications. The local A's number should be added first when updates are sent over an Egyptian network. Therefore, when A S 200 receives the BGP update, the A S path contains a value of 1200.
A S number 200 is set via manual manipulation, and the EA S number one is prepended automatically by GP. Because the update is sent over an EBGP session, when the edge router in AS 200 receives the BGP, it checks the AS path to verify that the BGP updates were not propagated accidentally by a routing loop, and the edge router finds its own AS number in the AS path. It assumes that the BGP update has already been included in S 200. According to the BGP specification, the update will be silently ignored. Now assume that A S for the manual manipulation used a different A S number, not its own and not A S number 200. Would a hundred now have accepted the update? The answer is yes. However, in this scenario, a problem would have appeared at the latest when the root finally reached the actual AS that belongs to the manually prepended AS number. This AS would reject the root because it would have found its own AS number somewhere in the AS path. How many copies of the AS number should you prepend to the AS path? The answer depends on the goals of the administrative policy. In the general case, it is not easy to determine the exact number of required AS numbers to propound because the sending AS does not know which native paths are available to other autonomous systems.
There is no exact mechanism to calculate the required projected S path length. If a primary and backup scenario is desired, use the long-preceded AS path over the backup length to show that the primary AS path will always be shorter. On every internet, a long backup path consumes memory. Experiment with various A-Spherical lenses until the backup link is idle. Add a few more AS numbers for improved security and unexpected changes in the Internet. If the traffic load distribution is satisfactory, begin with a shortened spot monitor link and gradually increase the pretended path length. Continuously monitor the link's usage and, if necessary, change the pretended AS path length. Here are two common scenarios in which the AS path can be used for pending action. establishing a primary or backup link as an announced backup-prepped route propagates through the Internet.
All the routers along the way that receive the route need to store it together with its AS path attribute. If this information is long, it will consume extra memory on these routers. However, routers forward only routes that are selected as the best among those that receive multiple alternative routes for a destination and will select the route with the shortest ASN for that route only when both the primary and secondary links are up. The neighbouring A's will receive two routes to the destination that differ only in the A's path length. The route with the shorter A-Spaw will then be advertised through If the primary link fails, the route with the longer A-S path is the only remaining route. As a result, the primary route is defined and the fictitious route is publicised on the Internet. Extra memory will be consumed on each Internet in this case due to the storage of the prepended data. The longer the announced A-S path is to the EDGP neighbour connected via the backup link, the less likely it is that incoming traffic will be received from that neighbor. You can make a guess as to how many s numbers to prepend. After the prepending is implemented, you have to examine the result. If the expected result is not achieved, you can change the configuration and prepend a few more copies of the AS number.
After a S path link generates the desired results, you may want to prepend a few more copies of the A S number to the S path. This action protects the customer from packets being routed over the backup link at a later stage when the topology between autonomous systems has unexpectedly changed, requiring a longer A-spath to reach the primary link. When distributing the offer-return traffic in a multihome scenario, there is no way to exactly predetermine the volume of traffic that will be received or a particular link. The traffic load on different links will change depending on where the centres are located, which autonomous systems they belong to, the network topology, and the way that different remote autonomous systems are interconnected. This may also change with the load distribution. Only constant monitoring and fine tuning will ensure that the desired results are achieved. In an attempt, you can prepare a router connected to an overuse link with only a few extra copies of the local AS number. After the network has had time to converge, you must check the change in load distribution.
Monitoring the load must be prolonged long enough to be statistically significant. If enough traffic has not moved from the overused to the underused link, you must prepare more copies of the local. Then the process of resending local routes and entering the results starts again. BGP traffic floor: when multiple connections between providers are equal, BGP attributes such as wait and local preference solve only half the problem. How to choose the right path out of the AAS question How can you make certain that the traffic takes the right path? The more complex half of the problem is how to get ENS's neighbouring autonomous systems to choose the correct return path back into the A system. The Med attribute gives a hint to external neighbours about the preferred path into an AS when multiple entry points exist. The Med attribute is a hint to external neighbours about the preferred path into an AS when multiple entries exist. You can use the Met to influence participant selection in AS S neighbors.An AS can specify its preferred pointusing the Med in outgoing EBGP updates. Outside of a receiving ASP, the med is not propagated. The value of the Med attribute is zero. The unit is called the metric in Cisco iOS software. Because the med is a weak metric at lower med values, it is more preferred. You can use the Met attribute to influence the route selection process and outgoing updates to A neighbors. In that A. S.
The Met attribute is useful only if there are multiple entry points. A S The Met attribute, which is sent to an external neighbor, will be seen only within that A sandbox. Because the default value of the Metabout is zero, a root that contains the Met attribute will not advertise that Met beyond its localA. A low value of the meta attribute indicates a more preferred path. The Met attribute is considered a weak metric in contrast with weight and local preference. Rato will prefer a path with the smallest Medvalue, but only if the vehicle preference, A path, and origin code attributes are equal. Using the Met may not result in the expected ringing. A modifies any of the stronger BGP truth mechanisms; the term that is used in Cisco's software for Med is "metric." Metric also applies to the set command in route maps, as well as to show and demand.
4. Describe BGP Communities
A community is a BGP attribute that may be added to any prefix. Communities are transitive or optional attributes, which means that BGP implementations do not have to recognise the attribute to pass it on to another. As BGP communities enable you to tag routes and show consistent filtering or a consistent route selection policy, you can tag routes in incoming and outgoing routing updates or when doing read distribution.
Any BGP router can filter routes in incoming or outgoing updates or select preferred routes based on communities. By default, communities are stripped of BGP updates. A 32-bit community value is split into two parts for easier reading form. The EA number and the AS that defines the community meaning are both found in high-order six. low-order 16 bits encode the purpose and local significance When a router receives a route that has been marked with a predefined community, it will perform a specific predefined action that is based on that community setting. There is no advertised BGP-speaking router in any other neighbor's tag prefix, including other IBGP routers.
No exports If a router receives an abridged community, it will only propagate that update to intraconfiguration external neighbors. The no export attribute is the most widely used predefined community attribute. No Export This community has a similar meaning to No Export, but it keeps a route within the local A or member A within the confederation. The route is not sent to external BGP neighbours or to intra-confederation external neighbors. This community is also known. The term "local" or "community" is used in situations where traffic engineering control over more specific needs is required, but its propagation is restricted only to transit providers and not peers. The community does not have goods from major vendors and might require manual implementation. Communities are applied to any BGP route by using an app. Other routers can then perform any action based on the tag community that is attached to the route. Route There can be more than one BGP community attached to a single route, but the routes by default remove communities from outgoing BGAs. BGP communities provide a mechanism for reducing BGP configuration complexity on a router that is pulling routing information distribution. It can be read as a 32-bit value or split into two portions.
A 32-bit number is formed by the four bytes representing an ASN for which the community is intended and the last two bytes as a value with any predetermined meaning and GP community value. They can be represented as an adecimal number, which is rare. A hexadecimal number in standard 216-bit decimal values is delimited by the letter A, which is the most common. The usable range of free to use communities ranges from zero to 65; 534 is equal to 65,535. Zurved scope is zero to zero through zero is to 65,535 and 65,135 is to zero through 65,535 is to 65.535. Well-known communities fall into this range. BGPP well-known communities and well-known communes fall into the "served range" group, and as opposed to "user-defined communities," they do have a specific meaning. A set of community values is predefined in RFC 1997 and RFC 3760. FiveCO devices also recognise the Internet community, which is not a standards-based, well-known community with a predefined value of zero is to zero. The Internet keyword is used in Cisco iOS software to match any community in the communities. In other words, the keyword is a catch-all statement at the end of the community list. BGP communities are attributes that group and filter routes.
Communities are designed to give you the ability to apply policies to large numbers of routes by using multiple clauses in the configuration of route maps. Community lists are used in this process to identify and filter routes by their common attributes. The community attribute is a 32-bit, optional BGP attribute that was designed to identify communities and apply routing decisions, redistribute traffic, and so on according to them. This community attribute allows for easy application of administrative policies. BGP communities provide a mechanism used to reduce BGP configuration complexity on a router while controlling the distribution of routing information. A set of commuters has been predefined. When a router receives a route that has been marked with a predefined community, the router will perform a specific predefined action that is based on that community setting as follows: no advertise If a router receives an up-carry from this community, it will not forward it to any neighbor. No Export If a router receives an update with this community, it will only propagate it to intra-confederation neighbors. External Neighbors the no export attribute most widelyused predefined community attribute local as this communityhas a similar meaning to no export, but it's a route within the local A Sor member A S within the confederation. The route is not sent to any external BGPS or intra-confederation neighbors.
Internet advertisers advertise this route to the Internet community. All routers have community attributes that are usually used between neighbouring autonomous systems. For the BGP communities to be globally unique, a public AS number should be part of the community value. For this reason, you can enter the community value as 216-bit numbers that are separated by a colon. The first number, 16 bits, should be the AS number of the AS that defines the community e value. The second number should be a value that is assigned a certain meaning and is indicative of a community's (Pvalueinto) local preference in the neighbouring state. You can also use communities internally within an S to ensure a wide routing policy, in which case the first 16 bits should contain the AS number of the lows. Do you employ cases for BGP communities? Using communities in a BGP network requires full deliberation from a network designer. Using communities to support your BGP policy, first define administrative goals.
Then design the route policy. To achieve administrative goals, design your community scheme to fit individuals' tag routes. Configure root tagging on entry points or let BGP neighbours tag the roots. Act on tags, configuration filters, and root selection parameters based on communities. Community lists are used for community matching within route maps. First, the routing administrative policy has to be set. For example, you need to figure out what to filter at what point and how to modify route attributes to influence traffic flows to suit company requirements. Often, the cost of routing traffic unlinked can be a deciding factor in creating a routing policy. Next, you have to design the community plan to fit the individual goals of the policy. When your policy is defined and the community scheme is in place and documented, the deployment of the committee system will be done by configuring route maps on your devices. This step will include the tagging of roots and acting on the tag.
Depending on the position of the router in the network and policy direction, A peer's or a group of peers' outbound policy will differ from their inbound policy. The community list is an important tool at your disposal for grouping communities, which is used in the overall process to identify and filter roots by their common attributes. Plan your community scheme thoroughly. It will be difficult to change once in production. Pay attention to character positioning rather than numbers easily passed with drug expressions. For example, community 650 XYZ can mean 650 is the S number. The general rule is to use only fields X, meaning area code, and E, meaning city number. Field ZZ is arbitrary for colour code and meaning. More than one community is required for a route that is so well documented. Design more schemes. You should make the effort to document the values and meaning of your communities in as much detail as possible. The subsequent changes might prove difficult once the network is in production.
For example, the community 600 is equivalent to twelve 345, which, if tagged at the point of origin, can be used to signal the rest of the BGP network that this router is from area one. You will be filtering policies based on the special meanings of City 23 and 45. You can assign multiple community values to a single route if required. It will appear as a series of units that are attached to a route, which will all be processed at peering points depending on your policy. Case Study of the BP Solution with Communities In this case study, each step is considered appropriate. Examples are provided. The corporate network is composed of the company headquarters and two dislocated branches that are connected by one link. ECATION has multiple sites or buildings that are connected with high-speed metro Ethernet links. The connection between the company orders and branch one is realised with one link, while branch two has a redundant connection to the headquarters location. To precisely control the routing information exchange between locations, BGP was selected as the routing protocol. Zine includes the use of multiple numbers and an EBGP running between the headquarters and branch locations.
Each location is free to use any IGPit it deems to be the best fit for the job. The figure does not represent the complete topology, just the results. For this example, the autonomous systems can include root reflectors or a full mesh topology, but it makes no difference in this case, so it will be omitted here. The focus will not be on the root exchange within any single goal. The important part is that roots will be tagged and they will be exchanged between autonomous systems. For this case study, the Ms will be placed on the edge of each AS, which is the most convenient place to enforce BGP policies. The policy is designed with these simple requirements. Color code all routes with communities' selected routes from branches; they should be reachable only from the headquarters and no other branches. Branches that are connected with multiple links to the waters should be able to influence the outbound and inbound parts without configuration or policy changes at the headquarters. The company requires all routes to be color-coded depending on the point of origin of the route. The policy gets a little stricter and specifies certain routes that should be accessible only from the headquarters. But no other branches connected with multiple links to the headquarters should be able to control both the inbound and outbound direction of the traffic on their own without the network administrators at the headquarters needing to change any settings on routers.
This action will be implied by the use of signalling communities, which will indicate that the required local preference for specifically tag routes must be set when they arrive at the headquarters routers. This way, branch two can influence the return path of the traffic and change the primary based only on its own router configuration. Influence route selection at the company headquarters for incoming routes and routes 5000 is to 99, set no export community, 650 is to 200, set local prints to 2650 is to 300, and set local preference to 300. It will be routed by company headquarters so that it begins with 650 at 5001 for site one, 1650 at 5002 for site two, and 650 at 5003 for site three. Branch one will tag the fact that it begins with 65; branch two is to 5101 for site 165; and branch three is to 5102 for site two. Branch two will tag the roots that it originates with: 65 and two are to be tagged to 5201 for site 165, two are to be tagged to 5200, and site two will also have a system in place that states that certain attributes of hardware routers are included in the boundaries of the tags set in the branch router as those that originate these routes.
If the branch routers tag their routes with 600 to 99, the headquarters ingress policy will state that no export community is permitted for the router, whereas if the branch routers tag their routes with 65 to 200, the headquarters ingress policy will set the local preference to 200 for this route. If Route 65 is to 300, the headquarters ingress policy will set the local preference to 300. BGP, Local Preference, and No Export In this example, you will consider the second point of your policy, which states that roots tagged at branches 650 to 99 will not be exported out of them, whereas roots tagged at branches 650 to 300 will be assigned a local preference of 203 to 100, respectively. when entering a 650. Always use the additive keyword router configuration if you've observed the existing communities when applying inbound policies and adding some new ones; otherwise, all community values will be overwritten. The green middle path shows the advertisements for Ten 02224 through the BGP network.
It will not be advertised beyond a 650 because it has sagged with the community, where 600 is to 99. The orange top path shows the Edwards of 100:1, which will also be marked as no export at the entry into 650 as a sequence and will not be advertised out to 650 and 2. The blue bottom shows the advertisements for Network Ten, 022-1024, which does not have any restrictions and, as such, will reach both the headquarters and Branch One. The green and blue routes will be tagged with 65300 at the top Branch Two router and with 650isto 200 at the bottom Branch II router. As a result of those routers, the headquarters will apply the respective local preferences, thus making the top path better for travel from the headquarters back to Branch Two.
If in the future Branch Two wishes to make the second link more desirable, it will put community tags between the top and bottom edge routers. This change requires no changes at the headquarters if the paw on the headquarters edge routers is properly set to recognise those communities and apply appropriate local preferences. The Community Lists feature in Cisco iOS, iOS XE, and iOS XR software introduces a new type of community list. The name "community list" BGP naming allows the network operator to assign meaningful names to community lists, and it increases the number of community lists that can be configured. Named community lists can be configured with regular expressions and with numbered community lists. There is no limitation on the number of community attributes that can be good for a named community list. The number of community lists that a network operator can configure increases because there is no limit on the number of named community lists that can be configured.
A named community list can be configured with regressions or with numbered community lists. The BGP named community list feature allows the network operator to give meaningful names to community lists. All rules for numbered communities apply to named community lists, except that there is no issue with the number of community attributes that can be configured for a named community list. Although both standard and community lists in the iOS XC software have a limitation of 100 community groups that can be configured within each type of list, a named community list does not have this limitation.
5. Designing a Dual-Stack MP-BGP Environment
The term "dual stack" is frequently used when discussing IPV6 deployment. Dual stack refers to running IPV four times in the router or device at the same time. This is considered the preferred method for converting from IPV4 to IP six.A dual-stack deployment places additional load on the routers in the network. There are increased risk source requirements for the MiBotthe IP and IPV6 routing tables. This includes separate ribs and fibs and the need for polite GPS with BGP. There is an increased memory requirement to maintain the additional prefix information.
There is no additional processing needed to maintain more BGP session peering. You should configure separate BGP sessions for I-4 and IPV-6 prefix information. This guarantees next-hop reachability for each address family in the BBGP for IPV6 deployment. Considerations The techniques and mechanisms provided by BGPV-4 are available in MP BGP for handling IPV-6 NLRI. The decision process, policy features, and scalability mechanisms are not specific to IPV-4 reachability. They apply to IPV6 as well. This means the route dampen, a route reflection discriminator, BGP confederations, outbound route filtering, and more. The same is true for MPBGP; BGP runs on top of TCP and is protocol-independent, as is IPV 4 and IPV 6. This means that the underlying network layer protocol can be either IPV 6 or IPV 6 with no changes to BGP. BGPmessages contain two fields: router ID and clusteri. Both are four bytes long.
The BGP open message contains a router ID field. This field is four bytes long. There is no requirement that this address be reachable or even an actual IPV4 address; only that it be a unique 32-bit number. The router automatically generates the router ID based on the IPV4 addressing configured on the router, the address given on the loopback interface, or if there is no loopback, the highest IPV4 address on any of the interfaces. In an unmixed IPV-6 deployment, no IPV-4 addressing is configured, providing nothing for the router to use for a router configuration. In this case, the router ID must be manually configured and the BGP process initiated. If there is no router ID, a BGP session will not be formed. The cluster component of BGP also requires a unique four-byte number used on reflectors. The cluster ID is carried in the NLIN and the BGP update messages. If a router ID is confusing the value that is used for the cluster ID, the cluster ID can also be configured independently of the router ID's originator ID attribute, which is also a four-byte value used with root reflection.
The value for the originator ID is provided by the manual configuration offering router ID. IPV 6 does not support autosummarization along class full boundaries. Because Pipv6 does not use address classes, the autosummary command has no effect on BGPv6 prefix information. Configuring MP BGP for IPV Six The BGP configuration for IPV Four and IPV Six is very similar, but when you configure IPV Six, the address family style configuration is required. That style of configuration is used for all the address families except IPV 4. By all accounts, IPV6 forwarding is disabled. This must be done explicitly in the Globe plug configuration mode by using the V-6 unique Castrooting command. The concept of defining allegiance relationships, or neighbors, in the main BGP router configuration underpins Vgpa Fstyle configuration.
These neighbours are then activated for each NLRI type that will be carried in the steering session. By default, the IPV4 NLRI is on for all the Psessions. You can disable the default behaviour of carrying IPV-4 NLRI on all BGP sessions using the NGP default IPV-4 unicorn command. The process of injecting IPV 6-prefix information into beaches is the same. for IPV Four. The configuration must be done under the IPV 6-AF configuration. The network command is used to redistribute prefix information from another routing protocol or inject prefixes from the routing table. The two primary methods for filtering and matching prefix information are prefix lists and access control lists. ACLs are the most common form of prefix or packet filtering is ACLs. When creating ACLs for IPV six prefix information, you must use named ACLs because numbered ACLs are not reported. The initial implementation of ACLs for IPV supported only matching against source and destination addresses. Support for matching against additional information was added in Cisco iOS release 12.2.
When you use ACLs for prefix filtering, only the source and destination are relevant, and wildcard bits are not supported. The prefix list functionality has been extended to support IPV six-root filtering. Just like IPV4 prefix lists, prefix lists with dipvs are used only for prefix filtering and not for packet filtering. The use of prefix lists and prefix ACLs is primarily used for packet filtering. A Dual Stack IPV Four and IPV Six Case Study This case study begins with a simple IPV Four network in a root reflection environment. The network is comprised of three core routers: Rone, R2, and R3. They are root reflectors and have a full IPGP mesh. There were also three reflector clients on the network: R 4, R 5, and R 6. Each router has an IPV4 loopback address for the IPP sessions. The loopback addressing scheme is 10 1 1 x 32, where x is the router number. This is the IGTP used for internal reachability for the BGP sessions. This IGP was chosen because it offers intended IPV-6 functionality. The routing protocol runs directly over the data link layer and does not run over IV and IPV Six. This enables IPV-4 and IPV-6 prefix information to be carried in the same protocol while maintaining network topology independence from IP version. The IPV6 BGP deployment follows the same topology. IPV Four network The core routers act as root reflectors for the IVC fixes.
The edge routers should be setup as root reflector clients. Here are apps for configuring the IPV-6 VGP network. Step One: If IPV6 forwarding is not enabled, IPX packets will not be routed. It is possible to configure IPV6 and have IPV6 routing information in the ruval, but packets will not be forwarded if forwarding is not enabled with the global configuration command. IPV-6 unicast routing Step 2: The BGP router ID should be manually set for each router. This also shows that if IPV is ever removed from the network, the IPV-6 BGP session will remain active while IPV-4 addresses are configured on the router. This does not cause a problem, but the removal of IPV4 can result in the failure of all IPV6 BG sessions. If the BGP router ID is not set, use the BGP router X command under the BP router configuration. Step three is to configure a loopback with an IPV6 address, just like IPV4 sessions. This will be used to form the MP BGP sessions. The configuration of addressing on all internal links is not necessary because link local addressing can be used for forwarding. To use link local addressing on the physical links, configure the IPV signal command under each interface to initiate the autocreation of the link local addresses. Global addressing is used for exposing links to provide a reachable next-hop address.
Step four is to enable the IPV Six IGP; this provides IPV Six packet capability across the entire network, allowing IPV Six BGP sessions to form. After that, they were configured. In this case study, IPV6-SIS is used under each interface, including the loopback phase. Step five is to configure IPV6 on the router. With this foundation in place, you can configure the six BGP sessions. This is done under the main BGP configuration after you configure the BGP session to activate the IPV6 address family configuration mode.
The IPV Six BGP network is now ready to tie prefix information and inject the IPV Six prefix information under the IPV Six address family configuration using redistribution or network commands. Also, BGP synchronisation must be disabled for IPV694 if synchronisation is not being used. Case study summary The subject of IPV-6 is extensive, and many standards detail its operation of IPV Six. From an operations perspective, BGP has been modified with IPV Six. With the MP BGP extension, the core of the BGP protocol remains unchanged, allowing you to continue your BGP experience. When you transition to IPV6, the only significant change is often the format of the address when deploying IPV6 alongside IPV4 in a dual stack deployment as the primary method of deploying IPV6.
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