Juniper JUNOSE 11.2.X BGP AND MPLS, Configuration Manual

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To configure router Topeka:
host3(config)# router bgp 25
host3(config-router)# neighbor 10.1.13.1 remote-as 604
host3(config-router)# network 172.31.64.0 mask 255.255.192.0
Additional configuration is required for routers Biloxi, Memphis, and Jackson; the details
depend on the IGP running in AS 604.
neighbor remote-as
•
Use to add an entry to the BGP neighbor table.
•
Specifying a neighbor with an AS number that matches the AS number specified in the
router bgp command identifies the neighbor as internal to the local AS. Otherwise, the
neighbor is treated as an external neighbor.
•
If you specify a BGP peer group by using the peerGroupName argument, all the members
of the peer group inherit the characteristic configured with this command unless it is
overridden for a specific peer.
•
This command takes effect immediately.
•
Use the no version to remove an entry from the table.
•
See neighbor remote-as.
Next-Hop-Self
In some circumstances, using a third-party next hop causes routing problems. These
configurations typically involve nonbroadcast multiaccess (NBMA) media. To better
understand this situation, first consider a broadcast multiaccess (BMA) media network,
as shown in Figure 29 on page 107.
Figure 29: Next-Hop Behavior for Broadcast Multiaccess Media
Routers Toledo, Madrid, and Barcelona are all on the same Ethernet network, which has
a prefix of 10.19.7.0/24. When router Toledo advertises prefix 192.168.22.0/23 to router
Madrid, it sets the next-hop attribute to 10.19.7.5. Before router Madrid advertises this
prefix to router Barcelona, it sees that its own IP address, 10.19.7.7, is on the same subnet
as the next hop for the advertised prefix. If router Barcelona can reach router Madrid,
then it should be able to reach router Toledo. Router Madrid therefore advertises
192.168.22.0/23 to router Barcelona with a next-hop attribute of 10.19.7.5.
Now consider Figure 30 on page 108, which shows the same routers on a Frame
Relay—NBMA—network.
107 Copyright © 2010, Juniper Networks, Inc.
Chapter 1: Configuring BGP Routing