From: Andrew Lissitz \(alissitz\) (alissitz@cisco.com)
Date: Sat Nov 05 2005 - 21:46:41 GMT-3
Hey, I still owe you comments on your last email! ... please pardon the
delay on my other response
You can route global traffic into a interface that belongs to a vrf; ip
route 10.0.0.0 255.0.0.0 inter fe1. This works
I have not tried to add a route to one vrf, and tell it to go down an
interface that belongs to another vrf. For your example "ip route vrf
up 20.0.0.0 255.255.255.0 fe1", I would have to try it. If you lab
this, be sure to add a route to the other vrf for return traffic so that
the route lookup on the 'far' side succeeds.
Also, traffic going from global to vrf or vrf to vrf can not have
overlapping destination addresses. VRFs keep these routes separate, but
when you start sharing or routing traffic into different VRFs then
address problems can arise.
The last route; ip route vrf abc x.x.x.x x.x.x.x global installs the
route in the vrf and allows the vrf to reference the global table for
resolution. If the destination lookup is actually in another VRF, as in
the example below, then the global table would not know about it. The
global route does not know about interfaces and routes in VRFs.
So using the global keyword is for traffic leaving the VRF and going
'global' ...
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Jongsoo
Sent: Saturday, November 05, 2005 7:27 PM
To: FORUM; C&S GroupStudy
Subject: IP route vrf command ( SP CCIE)
Let's say something like
CE1 10.1.1.1---------fe1- PE1- fe0-------CE2 10.1.1.1
In PE1,
ip vrf up
....
ip vrf down
....
Int fe1
ip vrf forwarding down
ip address 10.1.1.2 255.0.0.0
Int fe0
ip vrf forwarding up
ip address 10.1.1.2 255.0.0.0
"ip route vrf up 20.0.0.0 255.255.255.0 fe1"
I understand this static command installs a static route in the VRF "up"
routing table to forward destination address of ip packet matching
20.0.0.0/24 to fe1, which belongs to VRF down. It will generate ARP for
every different destination address, which consume memory.
"ip route vrf up 20.0.0.0 255.255.255.0 fe1 10.1.1.1"
a static route in the VRF "up" routing table to forward destination
address of ip packet matching 20.0.0.0/24 to 10.1.1.1 via fe1, which
belongs to VRF down. This won't require a recursive looking in VRF
down routing table because it knows outgoing interface ( of course
except for one time ARP only for 10.1.1.1)
ip route vrf up 30.0.0.0 255.255.255.0 10.1.1.1
installs a static route in the VRF "up" routing table to forward
destination address of ip packet matching 30.0.0.0/24 to 10.1.1.1.
This will require a recursive looking within VRF up routing table in
order to resolve the outgoing interface ( and one time ARPentry only for
10.1.1.1)
I can also think of
ip route vrf up 30.0.0.0 255.255.255.0 10.1.1.1 global
In this case, outgoing interface resolution occurs in global routing
table.
Seems straight forward but multiple static command get very complicated.
I guess "keep it simple" may be the rule of thumb when it comes to
multiple VRF...
Any comment welcome
Jongsoo
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