Re: BGP question.

  • To: Barry Raveendran Greene <bgreene at cisco dot com>
  • Subject: Re: BGP question.
  • From: Jumpot Phuritatkul <howdy at nectec dot or dot th>
  • Date: Thu, 19 Jun 1997 20:08:43 +0700 (GMT+0700)
  • Cc: "'apops at apnic dot net'" <apops at apnic dot net>, "'Scott Huddle'" <huddle at mci dot net>
  • In-reply-to: <01BC7CDB.693208A0 at bgreene-pc dot cisco dot com>
  • Sender: owner-apops@apnic.net
    • Thanks for your advice.
      
      I have a 7507 for B and 7513/VIP for C. at B, I have many networks that
      connected with many slots and I want them to use path 2)B-D-C except
      2 serial interface to two of my upstreams use path 1)A-B-C .
      
      Can you give me another solution by use BGP setting command?
      
      Jumpot-
      
      On Thu, 19 Jun 1997, Barry Raveendran Greene wrote:
      
      > Hello Jumpot,
      > 
      > This one is a little difficult. Your objective is the following:
      > 
      > 	1) A to go to C via path (1) A-B-C
      > 	2) B to go to C via path (2) B-D-C
      > 
      > Here's the problem. You have one forward table (i.e. sh ip route on a Cisco 
      > router). This will hold the route selected from the routing protocols. You 
      > can manipulate the route selection process (i.e. like using the local 
      > preference in BGP), but you will still only get the "best" entry in the 
      > forward table selected for use. When you have two "equal" cost entries in 
      > the forward table, Cisco "round robins" packets evenly over the two equal 
      > entries (this does not mean load balance since packets are not of equal 
      > size).
      > 
      > So all packets coming into a router will use the forward table to determine 
      > which interface to "forward" the packets.
      > 
      > Now for the possible "hack" that may work (not guaranteed) if you have a 
      > 7500 w/VIP cards. With Cisco's VIP architecture and distributed switching, 
      > forward tables are pushed out to the VIP processors. If you place the 
      > serial connection for "A" and "C" on the same VIP card. Put "B" on another 
      > VIP card with the LAN interfaces from B's site on that same VIP card the 
      > serial link from "D" (preferable on a different bus). Packets coming in 
      > from A will prefer the interface on the same VIP card - C. Packet from B's 
      > LAN interfaces will prefer the D interface.
      > 
      > I'm not sure that will work as described. Plus, this only takes care of 
      > traffic flows coming from A (downstream). For Internet traffic in Asia, 
      > that's 60%-80% for the traffic.
      > 
      > If you have a 7500 w/VIP card and you wish to pursue this hack, let me 
      > know.
      > 
      > Barry
      > 
      > 
      > Jumpot Phuritatkul wrote:
      > 
      > >But from my intention, B will announce C and D networks by originating
      > >from B because I don't want A to see AS C and D. So  that A will see C
      > >and D networks by only AS-path B .
      > >>From your solution, at B will get C's routes with 2 AS-path (C and D-C)
      > >and B will choose D-C to be the best path because of setting localprefs.
      > >Consequently, B will announce the best path of C to A with originating 
      > from B
      > >then A will see C'routes from B which was only one AS-path B and it is the 
      > >best  path that B send to A that is path (2) but I want A to go to B via
      > >path (1). How can I do ?
      > >
      > >				(1)
      > >	     [A] --------[B]----------------[C]
      > >        	          |    (2)           |
      > >                	  +------[D]---------+
      > >
      > >-Jumpot
      > >
      > >
      > >On Wed, 18 Jun 1997, Scott Huddle wrote:
      > >
      > >> If B localprefs D higher it will prefer that route to C
      > >> (and yet still have it if D goes down)  B can announce
      > >> C and D to A and it (A) will select BC over
      > >> BDC by virtue of path length.
      > >>
      > >> Did I miss something?
      > >>
      > >> -scott
      > >>
      > >> At 06:00 PM 6/18/97 +0700, Jumpot Phuritatkul wrote:
      > >> >Hi,
      > >> >	Would someone give me a solution for this problem?
      > >> >
      > >> >				(1)		
      > >> > 	[A] --------[B]----------------[C]
      > >> >		     |	  (2)		|
      > >> >		     +------[D]---------+
      > >> >
      > >> >	There are 4 networks of A, B, C and D.
      > >> >	A,B,C and D have their own Autonomous System Numbers.
      > >> >A is upstream provider of B. B want to announce B,C and D's networks 
      > with
      > >> >AS origin of B to A . I want A to go to C via path (1) A-B-C , and B to 
      > go
      > >> >to C via path (2) B-D-C . How can I set BGP command at B,C and D?
      > >> >Please help me solve this problem.
      > >> >
      > >> >Regards,
      > >> >Jumpot Phuritatkul
      > >> >Network Technology Lab.
      > >> >NECTEC, Thailand .
      > >> >
      > >> >
      > >> 
      > >_________________________________________________________________________
      > >> >To unsubscribe: send "unsubscribe" to apops-request at apnic dot net
      > >> 
      > >------------------------------------------------------------------------
      > >> >
      > >> >
      > >>
      > >
      > --
      > --
      > --
      > Barry Raveendran Greene                    |       ||        ||        |
      > Senior Consultant                          |       ||        ||        |
      > Corporate Consulting Engineering           |      ||||      ||||       |
      > tel: +65 738-5535 ext 235                  |  ..:||||||:..:||||||:..   |
      > e-mail: bgreene at cisco dot com                  |  c i s c o S y s t e m s  |
      > 
      > 
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