I test the BGP in my PC, this below is the topology:
R1--(eBGP)--R2--(iBGP)--R3
. and R2-R3-R4
are in OSPF(omit details).

this is my detail configuration of BGP:
[R1-bgp]dis this
#
bgp 100
peer 10.1.12.2 as-number 200
#
ipv4-family unicast
undo synchronization
network 100.1.1.1 255.255.255.255
network 100.1.2.1 255.255.255.255
peer 10.1.12.2 enable
#
return
[R2-bgp]dis this
#
bgp 200
peer 3.3.3.3 as-number 200
peer 3.3.3.3 connect-interface LoopBack0
peer 10.1.12.1 as-number 100
#
ipv4-family unicast
undo synchronization
network 2.2.2.2 255.255.255.0
network 10.1.23.0 255.255.255.0
peer 3.3.3.3 enable
peer 10.1.12.1 enable
#
return
[R3-bgp]dis this
#
bgp 200
peer 2.2.2.2 as-number 200
peer 2.2.2.2 connect-interface LoopBack0
peer 4.4.4.4 as-number 200
peer 4.4.4.4 connect-interface LoopBack0
#
ipv4-family unicast
undo synchronization
network 3.3.3.3 255.255.255.255
peer 2.2.2.2 enable
peer 4.4.4.4 enable
#
return
I have a question, you see in R3, the bgp routing-table
, the network 100.1.1.1/32
and 100.1.2.1/32
is not valid, so can not added into the ip routing-table
. but why it is invalid?
and the same thing, in R1 there is no R3's 3.3.3.3
in bgp routing-table
.