BGP use TCP. How ???

[fred_m]

Hy for all,

I've been study about BGP, and reading i found that bgp work with TCP. If router is Layer 3 (just IP) how bgp work with TCP Layer 4 ??

Tanks.

Fred

[ahmed-hussein]

Hello,

Actually the router understand layer 4 parameters like port numbers, but we call it layer 3 because its routing decision based on ip (layer 3), like switches we call it layer 2 devices because the switching decision based on layer 2 information

Thanks,

Ahmed Hussein

[nbhandarkar]

Hi,

BGP works at the Application Layer hence it has a well-known port number 179 to identify which application should handle these packets. BGP uses TCP windowing technique for packet exchange.

Yes, Router does work at Layer3. The primary function of a Switch is to forward frames which is Layer 2 function, hence we call the switch as Layer 2. The primary function of the router is routing packets to destinations which is Layer 3 function, hence we call it Layer 3.

Just like other applications such as TFTP(port69), Telnet(port23), etc work on the router, BGP also works on the router.

Pls do rate all helpful posts.

[ankurbhasin]

Hi Fred,

Long back in Jan 2005 I inititated the same string and was detailed by many experts, just have a look at the post

http://forum.cisco.com/eforum/servlet/NetProf?page=netprof&forum=Archive&topic=Network%20Infrastructure&CommCmd=MB%3Fcmd%3Dpass_through%26location%3Doutline%40%5E1%40%40.1dd7283c/0#selected_message

HTH,

Ankur