From: Scott Vermillion (scott_ccie_list@it-ag.com)
Date: Sat Dec 22 2007 - 18:00:19 ART
Matt,
Not sure if I followed exactly correctly, but in that last part, when you
set the advertised metric to 84 at R2, did you leave the default to Type 2?
If so, then you would have two E2 routes of variable cost, no? The behavior
would be expected in that case. Direct from the RFC:
"Type 1 external paths are always preferred over type 2
external paths. When all paths are type 2 external
paths, the paths with the smallest advertised type 2
metric are always preferred."
Cheers,
Scott
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of Matt
Sherman
Sent: Saturday, December 22, 2007 1:16 PM
To: ccielab@groupstudy.com
Subject: OSPF metric-type 1 becoming more preferred with a higher metric
Hello,
I'm having some problems determining why a certain route is put into the
routing table when it has a higher cost than one being received from another
router.
Here's the scenario. Router R4 is receiving redistributed EIGRP routes from
R2 and R3. If I advertise them equally it works as planned.
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***
R4#sh ip route 145.0.0.0
Routing entry for 145.0.0.0/22, 1 known subnets
O E2 145.0.0.0 [110/20] via 172.16.2.3, 00:01:36, Serial1/0
[110/20] via 172.16.2.2, 00:01:36, Serial1/0
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***
However if I set redistribution on R2 with a metric-type of 1, R2's route
becomes more preferred even though its metric is higher than R3's.
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***
R4#sh ip route 145.0.0.0
Routing entry for 145.0.0.0/22, 1 known subnets
O E1 145.0.0.0 [110/84] via 172.16.2.2, 00:00:30, Serial1/0
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***
I can see it being deleted from the route table
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***
*Mar 1 04:28:52.078: RT: ospf's 145.0.0.0/22 (via 172.16.2.2) metric
changed from distance/metric [110/20] to [110/84]
*Mar 1 04:28:52.082: RT: del 145.0.0.0/22 via 172.16.2.3, ospf metric
[110/20]
*Mar 1 04:28:52.086: RT: NET-RED 145.0.0.0/22
*Mar 1 04:28:52.086: RT: NET-RED 145.0.0.0/22
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***
If I manually specify the same metric of 84 on R2, the router goes back to
preferring R3's route with a metric of 20.
redistribute eigrp 200 metric 84 subnets
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***
*Mar 1 04:32:15.950: RT: del 145.0.0.0/22 via 172.16.2.2, ospf metric
[110/84]
*Mar 1 04:32:15.954: RT: delete subnet route to 145.0.0.0/22
*Mar 1 04:32:15.958: RT: NET-RED 145.0.0.0/22
*Mar 1 04:32:15.958: RT: delete network route to 145.0.0.0
*Mar 1 04:32:15.962: RT: NET-RED 145.0.0.0/16
*Mar 1 04:32:15.966: RT: SET_LAST_RDB for 145.0.0.0/22
NEW rdb: via 172.16.2.3
*Mar 1 04:32:15.970: RT: add 145.0.0.0/22 via 172.16.2.3, ospf metric
[110/20]
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***
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