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: Sun, 22 Jun 1997 02:32:14 +0700 (GMT+0700)
  • Cc: "'apops at apnic dot net'" <apops at apnic dot net>
  • In-reply-to: <01BC7E71.A17D9F20 at bgreene-pc dot cisco dot com>
  • Sender: owner-apops@apnic.net
    • Hi Barry,
      
      Thanks, I will try to test it.
      
      Jumpot.
      
      On Sat, 21 Jun 1997, Barry Raveendran Greene wrote:
      
      > Hello Jumpot,
      > 
      > Here's the policy routing option. I need a little time to check a config 
      > with my colleagues.
      > 
      > Here's a example config for Router B (RTB). I'm guessing on your config, so 
      > I picking thing out of the air. Instead of IP addresses, I'm using '[Router 
      > A]' to describe the link. delete the '[Router A]' and fill in with the real 
      > IP addresses.
      > 
      > !
      > interface serial 0/0
      > description LINK TO ROUTER A (Upstream)
      > ip address [Router A]
      > ip policy route-map Upstream_Policy
      > !
      > interface serial 0/1
      > description LINK TO ROUTER C (Down Stream Customer)
      > ip address [Router C]
      > !
      > interface serial 0/2
      > description LINK TO ROUTER D (National IXP)
      > ip address [Router D]
      > !
      > interface ethernet 1/0
      > description LINK TO LOCAL LAN
      > !
      > access-list 1 permit any [C's CIDR block]
      > !
      > route-map Upstream_Policy permit 10
      >  match ip address 1
      >  set ip next-hop [Router C]
      > !
      > !
      > 
      > This policy routing example will take all the packets from A that match an 
      > address in C's CIDR block and forward them out C's interface. All other 
      > traffic will use the forward table. Hence, you can set the BGP local 
      > preference for C's CIDR block to use D.
      > 
      > So this give you:
      > 
      >  	1) A to go to C via path (1) A-B-C (Achieved with policy routing)
      > 
      > 	2) B to go to C via path (2) B-D-C (Achieved with BGP local pref)
      > 
      > Barry
      > 
      > 
      > Jumpot Phuritatkul wrote:
      > 
      > >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  |
      > >>
      > >>
      > >
      > --
      > --
      > --
      > 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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