RE: recursive routing with a tunnel

From: Scott Morris (swm@emanon.com)
Date: Wed Sep 22 2004 - 17:26:51 GMT-3


That would be a perfectly reasonable way to do things. The end number used,
of course, would depend on what the existing metrics actually looked like.

 
Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713, CISSP,
JNCIP, et al.
IPExpert CCIE Program Manager
IPExpert Sr. Technical Instructor
swm@emanon.com/smorris@ipexpert.net
http://www.ipexpert.net
 
 

-----Original Message-----
From: Wang Dehong-DWANG1 [mailto:Dehong.Wang@motorola.com]
Sent: Wednesday, September 22, 2004 2:38 PM
To: 'swm@emanon.com'; ccielab@groupstudy.com
Subject: RE: recursive routing with a tunnel

Scott

Thanks for the response and it really make sense.. Don't have a lab right
now and can not try it now any more. I did try to play with AD and metrics
but for some reasons I failed to make it work. Since only OSPF is used, I
thought that putting "ip ospf cost 30000" under both tunnels might work, but
it seemed R3 think it is directly connected net and use 0/0(could be wrong,
can not remember the detail logs any more). Should this be the way to
manipulate the metric?

R3 Router:
========
int tunne1
   ip ospf cost 30000 <=== play with cost
  
R1 Router:
=========
int tunn 1
  ip ospf cost 30000

Thanks again.

-----Original Message-----
From: Scott Morris [mailto:swm@emanon.com]
Sent: Wednesday, September 22, 2004 12:42 PM
To: Wang Dehong-DWANG1; ccielab@groupstudy.com
Subject: RE: recursive routing with a tunnel

You do anything that is necessary to make sure that even after the tunnel is
up (and whatever new routing peering is up) the route to the "tunnel
destination" is NOT going to be preferred to come through the tunnel.

If the routing protocol is the same in and out of the tunnel, metrics may be
used... If you have two different routing protocols, then AD is a good
choice to use. Distribution lists may also be something to consider making
sure that the 'tunnel destination' route doesn't come into the routing
protocol on the tunnel.

HTH,

 
Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713, CISSP,
JNCIP, et al. IPExpert CCIE Program Manager IPExpert Sr. Technical
Instructor swm@emanon.com/smorris@ipexpert.net
http://www.ipexpert.net
 
 

-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of Wang
Dehong-DWANG1
Sent: Wednesday, September 22, 2004 12:30 PM
To: ccielab@groupstudy.com
Subject: recursive routing with a tunnel

I knew that this has been posted before.. but would like to ask it again..
Here is the scenario.
 
R4 ------- (area 4 ) -----R3---( serial link, area 2 )----------
R2--------(serial link, area 3) ----------- R1------- (area 0)
 
R3 serial link IP: 172.16.2.3
R1 serial link IP: 172.16.3.1
 
R3 Router:
========
int tunne1
   ip add 172.16.15.3 255.255.255.0
   tunnel destination 172.16.3.1
   tunnel source 172.16.2.3
 
R1 Router:
=========
int tunn 1
  ip add 172.16.15.1 255.255.255.0
  tunn destination 172.16.2.3
  tunn source 172.16.3.1
 
R1 connects to area 0, a virtual link was also created between R1 and R2 to
learn the routes from area 2. I also built a tunnel between R3 and R1
through area 0 so all the routes in area 4 can be learned as well. I created
additional interface on both R1 and R3 and then put them under ospf area 0.
It hit the recursive routing.. R3 sees a directly route through 172.16.15.0
subnets and then started to delete routes learned through serial interface,
which brought the tunnel interface down..
 
I am thinking of manipulating the distance which make some routes prefer
serial link and some use tunnel, but do not know exactly how.. Your helps
are highly appreciated..
 
thanks in advance.
 
- Dehong



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