Re: EIGRP distribute-lists with route-maps

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>
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
>
> 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.
>
> sh ip ro | s 200.2.2.0
> D 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
> 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 - 10:27:38 ART