before bgp works source & dest router should be reachable so in order

[krahulbgp]

Like before bgp works source & dest router should be reachable so in order to make different network reachable in bgp Does network commands(network x.x.x.x mask y.y.y.y) work to make it reachable " if not how to make reachable

[Jon Marshall]

The BGP peers need to be reachable before you can set any BGP configuration up and that includes any network statements. 

For EBGP usually the peers are directly connected but if they are not eg. you are peering on loopbacks then you would need static routes so the peers can ping each other first. 

Jon

[MHM Cisco World]

Noooooo

Bgp not like other protocol 

For example to make ospf between two peer config network between peer under ospf and ospf start work

Bgp is like tunnel the source destination of tunnel must known by other protocol or direct connect and then bgp start work, the network under bgp USE to learn each peer what found behind other peer (what attach)

[Flavio Miranda]

Hi

 Only directed connected network can be adviertised using the

network 

command. If you already formed  peering with

neoghbor

command.

 Remotes network does not require

network

command. 

[krahulbgp]

what to do to make a different network reachable in BGP  ?

[Jon Marshall]

Not really sure what you are asking. 

If you want to BGP peers to talk to each other then they need to be able to ping each other. 

Once you have done that for networks you want to advertise you can use the network command or you can redistribute. 

Perhaps you can clarify what you are trying to do ? 

Jon

[krahulbgp]

network

command is used to for direct connected prefix but when we have not direct connect than how o to make reachable ?

[Flavio Miranda]

You just need the BGP peering. BGP works like this. Once you form peering, unless you have some prefix-list blocking, you are going to receive your neighbor routing table and those network will be reachable.

That´s why you need to be carefull by configuring BGP. Depending on the neiighbor routing database, you can crash your router.

[MHM Cisco World · Accepted solution]

@Jon Marshall  statement explain in below  

In BGP network there are 

always BGP
if both Peer is direct connect no need IGP
if both Peer is indirect connect need IGP like OSPF EIGRP or static route, I know here you will confuse so if I use IGP then why we need BGP???
simply the IGP only connect LO use for BGP connection 
like 

router bgp x
neighbor LO-otherPeer
neighbor LO-otherPeer update source LO-thiePeer
net OTHERNET mask OTHERNET

we use IGP to make LO-otherPeer & LO-thiePeer are reachable 

[krahulbgp]

this is clear explanation  thanks

But in below topology  how R1 &R3 are  reachable without igp ,they made it  reachable 

 

[MHM Cisco World]

R2 - R3 is BGP 
R1 from view of R2 is like any network connect to R2 this is why it reachable, 
I answer you for previous post, make second review of my answers.
check R1 is it learn via BGP  from R2?

[Flavio Miranda]

Hi

  Network reachable means the network is on the routing table. Once you stablish the bgp neighborhood, you are going to receive the neighbor networks and they will be reachable.