Re: EIGRP distribute-lists with route-maps

One more thing. If you wanted to use a route map to affect the metric of a route you would apply it to the neighbor command inbound as you receive the route.

Jeffrey Lodwick - CCIE 15671 R&S
Senior Data Engineer / Owner
Jeff_at_tydesystems.com
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<div>-------- Original message --------</div><div>From: Billy Singh <billysingh_at_ipanyany.com> </div><div>Date:07/26/2014 8:46 AM (GMT-07:00) </div><div>To: "Tim Cribbs Jr." <tmcribbs_at_gmail.com> </div><div>Cc: ccielab_at_groupstudy.com </div><div>Subject: Re: EIGRP distribute-lists with route-maps </div><div>
</div>Bandwidth and delay. R4 is connecting to both upstream routers via the
same outgoing interface, i.e. e0/0, so I'm not following...

I disagree with the simple view that any time you use a route-map you're
doing PBR. Route-maps may be a functional component of PBR, but by
themselves I don't imagine they'd constitute PBR. The routing is still
being done by R4 using the RIB. PBR would be if packets were routed
before the RIB was consulted, no? If I'm manipulating the routes before
they enter the EIGRP topology table, therefore changing how they enter
the RIB that's not PBR.

On 07/27/14 00:27, Tim Cribbs Jr. wrote:
> Ask yourself what does EIGRP use (the defaults) to decide the best
> route. 2 metrics should come to mind. Using route-maps is PBR, which
> is prohibited. The answer is easier than you think.
>
>
> On Sat, Jul 26, 2014 at 10:18 AM, Billy Singh <billysingh_at_ipanyany.com
> <mailto:billysingh_at_ipanyany.com>> wrote:
>
> Good evening all,
>
> I was doing some practise labs tonight and playing around with EIGRP.
> I'm trying to grasp a better understanding of the limits of route-maps
> when used with distribute-lists in EIGRP.
>
> For the sake of simplicity, let's imagine a topology with three
> routers
> all connected over a shared, broadcast media (Ethernet).
>
> R2 & R3 are the upstream routers both advertising a network
> 200.2.2.0/24 <http://200.2.2.0/24>
>
> R4 is the downstream router with EIGRP neighbour adjacencies to both
> these upstream routers. As a result, R4 is doing equal cost
> load-balancing between both upstream routers for 200.2.2.0/24
> <http://200.2.2.0/24>.
>
> sh ip ro | s 200.2.2.0
> D 200.2.2.0/24 <http://200.2.2.0/24> [90/1024640] via 10.1.1.3,
> 00:00:16, Ethernet0/0
> [90/1024640] via 10.1.1.2, 00:00:16, Ethernet0/0
>
> The requirement was to have R4 prefer the route via R2, unless R2 was
> unavailable, in which case it would route through R3.
>
> - Configuration can only be done on R4.
> - No PBR (Policy Based Routing).
> - No manipulation of the Administrative Distance (AD) allowed
> (This was
> actually the easy answer, but I wanted to try and find an
> alternate method).
>
> So we can use route-maps in conjunction with distribute lists and I
> guess this is where my confusion currently is. Here's what I tried
> to do:
>
> 1. Access list to match the route:
>
> access-l 44 permit 200.2.2.0 0.0.0.255
>
> 2. Access list to match one of the route-sources (R3):
>
> access-l 3 permit host 10.1.1.3
>
> 3. Route-map configuration. I'm trying to bump up the metric of a
> route
> by 1000 so it's no longer the preferred route:
>
> route-map PREFER-R2 permit 10
> match ip addr 44
> match ip route-source 3
> set metric +1000
> route-map PREFER-R2 permit 20
>
> 4. Apply it to the EIGRP routing instance:
>
> router eigrp AS100
> addr ipv4 uni auto 100
> topo base
> distrib route-map PREFER-R2 in
>
>
> And it didn't end up working. So clearly my intended use of the
> route-map in the above scenario is invalid. Probably fine for when
> redistributing, but not when used in conjunction with distribute
> lists.
> If I add a different "set" parameter (one which seems to be commonly
> referred to in the configuration guide; a route tag), then I see
> that it
> gets applied:
>
>
> sh ip ro 200.2.2.0
> Routing entry for 200.2.2.0/24 <http://200.2.2.0/24>
> Known via "eigrp 100", distance 90, metric 1024640
> Tag 200, type internal
> Redistributing via eigrp 100
> Last update from 10.1.1.3 on Ethernet0/0, 00:00:13 ago
> Routing Descriptor Blocks:
> * 10.1.1.3, from 10.1.1.3, 00:00:13 ago, via Ethernet0/0
> Route metric is 1024640, traffic share count is 1
> Total delay is 1002 microseconds, minimum bandwidth is
> 10000 Kbit
> Reliability 255/255, minimum MTU 1500 bytes
> Loading 1/255, Hops 1
> Route tag 200
> 10.1.1.2, from 10.1.1.2, 00:00:13 ago, via Ethernet0/0
> Route metric is 1024640, traffic share count is 1
> Total delay is 1002 microseconds, minimum bandwidth is
> 10000 Kbit
> Reliability 255/255, minimum MTU 1500 bytes
> Loading 1/255, Hops 1
>
> I'm looking through the configuration guide and the CLI reference
> to try
> and work out what match criteria and set commands are available when
> route-maps are used under different contexts, but I'm not having much
> luck finding anything thorough or concrete. When you think about
> it, it
> does kind of make sense, distribute-lists are for filtering not
> routing
> metric manipulation but since route-maps allow for so much
> manipulation
> of routes an understanding of what parameters you can use under what
> scenarios would be great.
>
> Ideas or resources?
>
> Thanks.
>
> Billy
>
>
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Received on Sat Jul 26 2014 - 09:26:36 ART