he starts off slow... it's like being brand new again...
rta#sh run | b router
router ospf 10
network 172.16.0.0 0.0.255.255 area 0
!
router bgp 3
bgp log-neighbor-changes
neighbor 172.16.1.2 remote-as 3
neighbor 172.16.1.2 update-source Loopback0
neighbor 172.16.20.1 remote-as 1
!
he mentions turning on ip classless and no auto-summary... somebody forgot to tell him it's not 2000 anymore... this is a very good book... it would be nice if they revised it, like doyle did for routing tcpip...
i'll give his line by line of the pertinent commands, unless of course, you already know everything...
router process
[process-id]
This is a global command that defines a process such as OSPF, RIP, or
BGP and gives the process a process ID. Some processes, such as RIP,
do not require a process ID. For example, in RTA's configuration,
router ospf 10 indicates an OSPF process with ID 10, whereas router
bgp 3 indicates a BGP process in autonomous system 3.
network
This command indicates the networks or, in the case of OSPF, the
interfaces that will participate in a specific routing process.
etc...
rtf#sh run | b router
router ospf 10
network 172.16.0.0 0.0.255.255 area 0
network 192.68.0.0 0.0.255.255 area 0
!
router bgp 3
bgp log-neighbor-changes
neighbor 172.16.2.254 remote-as 3
neighbor 192.68.12.1 remote-as 2
neighbor 192.68.12.1 ebgp-multihop 2
rtf#sh tcp brie all
TCB Local Address Foreign Address (state)
695BAA54 172.16.1.2.179 172.16.2.254.60797 ESTAB
6874F178 0.0.0.0.179 192.68.12.1.* LISTEN
695B979C 0.0.0.0.179 172.16.2.254.* LISTEN
rtf#sh ip bgp neigh | i BGP
BGP neighbor is 172.16.2.254, remote AS 3, internal link
BGP version 4, remote router ID 172.16.2.254
BGP state = Established, up for 00:04:04
BGP table version 1, neighbor version 1/0
BGP neighbor is 192.68.12.1, remote AS 2, external link
BGP version 4, remote router ID 0.0.0.0
BGP state = Idle
BGP table version 1, neighbor version 1/0
External BGP neighbor may be up to 2 hops away.
note rte isn't lit up yet... there is no configuration in the book...
In RTF's configuration, you can see the ebgp-multihop 2 command being used as part of the neighbor configuration. This indicates that the exterior BGP peer is not directly connected and can be reached at a maximum of two hops away. Remember that ebgp-multihop is applicable with only EBGP, not IBGP. Also, the value at the end (2 in this example) represents the TTL (Time To Live) value to be configured in the IP packet header.
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