Routing
Highlighted
Routing

BGP states / TCP

‎10-07-2017 03:47 AM

Hi, struggling to see at what stage TCP fits into the overall BGP state process. I know it's the first thing that happens, but does it come before Idle or before Active for example or does it function alongside these and how?

 

In essence, where does TCP fit in in the state process - also is it continuous through the state process or does it stop at one of the states?

 

 <<< TCP here?

IDLE  <<< TCP here?

CONNECT <<< TCP here?

ACTIVE <<< TCP here?

OPENSENT

OPENCONFIRM

ESTABLISHED

 

Ive looked at plenty of documents but still struggling....

 

 

 

2 REPLIES 2
Highlighted
Routing

Re: BGP states / TCP

‎10-07-2017 04:00 AM

The only state that is not communicating via tcp is idle.  This is a pretty good listing of what each state is doing in the BGP process here.

 

https://www.juniper.net/documentation/en_US/junos/topics/task/configuration/bgp-transition-events-lo...

Steve Puluka BSEET - Juniper Ambassador
IP Architect - DQE Communications Pittsburgh, PA (Metro Ethernet & ISP)
http://puluka.com/home
Highlighted
Routing

Re: BGP states / TCP

‎10-11-2017 03:54 AM

Look up BGP FSM and aklso the rfc for BGP are excellent sources


@mozmarr wrote:

Hi, struggling to see at what stage TCP fits into the overall BGP state process. I know it's the first thing that happens, but does it come before Idle or before Active for example or does it function alongside these and how?

 

In essence, where does TCP fit in in the state process - also is it continuous through the state process or does it stop at one of the states?

 

 <<< TCP state is in relation to BGP peers

Peer 1 IDLE  <<<  NO TCP state>>> Peer 2

Initialize BGP resources on Peer 1 - start the ConnectRetry timer try to establish a TCP connection

Peer 1 CONNECT <<< TCP  here: waiting for the TCP connection to be completed >>> Peer 2

Peer 1 ACTIVE <<< TCP here: ConnectRetry time expire before TCP complete - try again to acquire a peer by initiating a TCP connection >>>Peer 2 If TCP successful, it clear ConnectRetry timer send an OPEN message to Peer 2

TCP onnection Established, time for BGP to be established

OPENSENT - wait for OPEN message response from Peer 2

OPENCONFIRM - OPEN message recieved, all is good, wait for KEEPALIVE or NOTIFICATION message. If KEEPALIVE  received, all is good go BGP established; if NOTIFICATION message recieved, tear down connection go back to IDLE

ESTABLISHED  - all is goo - then exchange routes

 

Ive looked at plenty of documents but still struggling....

 

http://www.freesoft.org/CIE/RFC/1771/31.htm

 https://www.juniper.net/documentation/en_US/junos/topics/reference/command-summary/show-bgp-neighbor...

 

 


CONNECT <<< TCP here

ACTIVE <<< TCP here

[KUDOS PLEASE! If you think I earned it!
If this solution worked for you please flag my post as an "Accepted Solution" so others can benefit..]
Feedback