Update-source specifies the interface which should be used as the source of all BGP packets originated by the router. show ip bgp summaryĮxplaining some of the above commands we used for the BGP configuration: Notice how the router has “rearranged” the BGP configuration, separating the generic from the address-family specific configuration.Ĭheck that the BGP sessions are up on both sides. Once the configuration has been entered, check the configuration as displayed by the router: show run | begin router bgp Many network operators using Cisco IOS routers use peer-group to scale their BGP configurations. There is a Cisco IOS configuration scaling feature called a peer-group. What needs to change from the above configuration example?Īlso, what do you think the configuration for CX2 would look like? Is it similar? What is different? The instructors will discuss this in class during the exercise. You need a similar configuration for BX2 peering with CX1. Neighbor 2001:db8:X::1 description iBGP with BX1 Neighbor 2001:db8:X::1 update-source loopback 0 Neighbor 100.68.X.1 description iBGP with BX1 Neighbor 100.68.X.1 update-source loopback 0 What needs to change from the above configuration example? You need a similar configuration for BX1 peering with CX1. Neighbor 2001:db8:X::2 description iBGP with BX2 Neighbor 2001:db8:X::2 update-source loopback 0 Neighbor 100.68.X.2 description iBGP with BX2 Neighbor 100.68.X.2 update-source loopback 0 If you cannot ping them, there is no possibility that the BGP session will come up! We have three routers in our Group, so we need to set up iBGP between all three - which means that each router will have two iBGP neighbours.įirst, make sure that you can ping the other routers using their loopback addresses. This must be done in all future BGP configurations of this workshop.Īs you will remember from the presentation, iBGP needs to be fully meshed. The command to do this is the distance bgp subcommand: distance bgp Įnable logging of BGP neighbour state changesĬonfigure deterministic calculations of MEDsĭisable the automatic exchange of IPv4 unicast routes on every peering session. To protect against accidents, the eBGP distance is set to 200 also. This means that there is a potential for a prefix learned by eBGP to override the identical prefix carried by IS-IS. On Cisco routers, the default distance for eBGP is 20, the default distance for iBGP is 200, and the default distance for IS-IS is 115. The Cisco IOS defaults are not optimised, so before we bring up BGP sessions, we should set the parameters that we require. IBGP Configuration Enable the BGP processīefore we set up iBGP, we need to do some basic preparation on the router. Refer to the IP Address Plan document for information about the IP address plan for the network infrastructure for these labs. Note: Actually, if everyone configured their IS-IS and static routes properly in the previous exercise, you should be able to ping all other routers in the lab using their loopback address. Ping your neighbour routers in other ASs using their point-to-point link addresses. Ping your neighbour router in the same AS using its loopback address (both IPv4 and IPv6!). This exercise builds upon the configurations implemented in the IS-IS + Static routing lab. Set up Internal BGP (iBGP) within the each Group autonomous system to carry routing information within the AS.
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