topic Basic BGP neighborship question in Routing

Basic BGP neighborship question

historicalswimming — Thu, 27 Jan 2022 17:42:51 GMT

Hello guys,

I am new to BGP and i would appreciate if someone can give me a hint on what is wrong with my config
Here is the topology

R1(BGP Router AS1) ----- R2 ------ R3(BGP Router AS2)

i wanted to make R1 and R3 BGP neighbors. All routers are connected with Ethernet links
According to the topology they are not directly connected since they have R2 between them (R2 does not have any routing protocols activated).
R1 has a static route to R3 network via R2 and R3 has a static route to R1 network via R2.
Ping is working between R1 and R3.
After going through the most basic config for BGP , when typing the neighbor command in both routers they fail to become neighbors ,actually they dont even try. I took a packet capture on R3 and R1 and i do not see any of them initiating BGP sessions.

The config on

R1: 

router bgp 1

address-family ipv4 unicast

bgp router-id  (R1's router id)

neighbor  (R3's ip address)







R3:

router bgp 3

address-family ipv4 unicast

bgp router-id  (R3's router id)

neighbor  (R1's ip address)

Can someone explain what am i doing wrong?

Re: Basic BGP neighborship question

MHM Cisco World — Thu, 27 Jan 2022 17:46:02 GMT

router bgp 1
neighbor R2 remote-as 3
neighbors R2 ebgp-multihop

ip route R2 serial or ethernet <-need this static route

R2

router bgp 3
neighbor R1 remote-as 1
neighbor R1 ebgp--multihop

ip route R1 serial or thereat <-need this static route

Re: Basic BGP neighborship question

Georg Pauwen — Thu, 27 Jan 2022 17:56:34 GMT

Hello,

you need to add ebgp multihop:

R1:

router bgp 1

address-family ipv4 unicast

bgp router-id (R1's router id)

neighbor (R3's ip address) ebgp-multihop 3

R3:

router bgp 3

address-family ipv4 unicast

bgp router-id (R3's router id)

neighbor (R1's ip address) ebgp-multihop 3

Re: Basic BGP neighborship question

historicalswimming — Thu, 27 Jan 2022 17:58:32 GMT

When i get to type this command

neighbor (R3's ip address) ebgp-multihop 3

this is the console message  "% Specify remote-as or peer-group commands first"

so i tried to do it like this

neighbor R3-ipaddress R3-AS ebgp-multihop 3 and then it give me an "Invalid input detected at '^' marker where the ebgp starts
valid"

Re: Basic BGP neighborship question

Richard Burts — Wed, 26 Jan 2022 17:23:18 GMT

Before you try the multi hop command you need to define the remote AS for the peer

neighbor R3 remote-as 3

Re: Basic BGP neighborship question

MHM Cisco World — Wed, 26 Jan 2022 17:25:03 GMT

correct the AS number.

Re: Basic BGP neighborship question

Georg Pauwen — Thu, 27 Jan 2022 18:05:46 GMT

Hello,

R1:

router bgp 1
address-family ipv4 unicast
bgp router-id (R1's router id)
neighbor (R3's ip address) remote-as 3
neighbor (R3's ip address) ebgp-multihop 3

R3:

router bgp 3
address-family ipv4 unicast
bgp router-id (R3's router id)
neighbor (R1's ip address) remote-as 1
neighbor (R1's ip address) ebgp-multihop 3

Re: Basic BGP neighborship question

Georg Pauwen — Thu, 27 Jan 2022 17:47:20 GMT

Hello,

does this actually work ?


R1
router bgp 1
neighbor R2 remote-as 3
neighbors R2 ebgp-multihop

ip route R2 serial or ethernet <-need this static route

R2
router bgp 3
neighbor R1 remote-as 1
neighbor R1 ebgp--multihop

ip route R1 serial or thereat <-need this static route

I was under the impression that there was no BGP configured on R2:

--> (R2 does not have any routing protocols activated).