BGP questions

Unanswered Question
May 20th, 2008
User Badges:

Guys we use static routes in bgp??? like what ar ethe things which force us to use static routes.....secondly when we put network under bgp command like bgp 123 netwrok 192.168.0.1 255.255.255.0 so the router starts advertising the network to its peer?? am i right? just like other routing protocols? thridly what eigrp and ospf uses as its transport layer protocol like bgp uses 179? which ports other routing protocols uses....guys thanks a million in advance

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 5 (2 ratings)
Loading.
Jon Marshall Tue, 05/20/2008 - 23:27
User Badges:
  • Super Blue, 32500 points or more
  • Hall of Fame,

    Founding Member

  • Cisco Designated VIP,

    2017 LAN, WAN

Static routes in BGP can be used to advertise out networks. For example if you have under your BGP config


router bgp 65321

network 192.168.5.0 mask 255.255.255.0


and in your routing table you have


192.168.5.0 255.255.255.128

192.168.5.128 255.255.255.128


then it will not be advertised out because BGP needs an exact match in the IGP routing table to advertise a route out from it's network statement. So you could put


ip route 192.168.5.0 255.255.255.0 Null0


into the IGP table and then BGP would advertise it out. Alternatively you could just not include the "mask 255.255.255.0" part of the network statement and then as long as there is a part of the route in routng table it will be advertised out (thanks to Victor for pointing that last bit out).



You are correct in that if you have


router bgp 65321

network 192.168.5.0 255.255.255.0


then BGP will advertise this network out to other peers (subject to above provisos).

However this is not how IGP routing protocols (RIP/EIGRP/OSPF) work. For example


router eigrp 1

network 192.168.5.0


This does not tell EIGRP to advertise out network 192.168.5.0. What it does do is tell the router to start running EIGRP on any interface that has an ip address out of the 192.168.5.0 subnet.


EIGRP & OSPF work at L3 of the OSI model. They have their own IP protocol numbers


EIGRP 88

OSPF 89


so they do not have a TCP port number.


Jon



lamav Wed, 05/21/2008 - 18:17
User Badges:
  • Blue, 1500 points or more

Jon specializes in 'lovely.' :-)


Rated your post, Jon....I loved it.


Victor

Actions

This Discussion