From: gladston@br.ibm.com
Date: Mon Apr 18 2005 - 16:11:05 GMT-3
R1, R2 and R3 are connected to Vlan 200.
R1 and R2 are also connected to Vlan 400. They speak OSPF, area 0, on Vlan 400.
R2 has a default route point to R3's IP address on Vlan 200. R2 is generating default on OSPF, and forwarding this to R1 through Vlan 400.
R1 does not install 0.0.0.0.
'Troubleshooting IP Routing Protocols' explains two reason why routes are not installed:
- Forward address known by external LSA
- Missing Summary LSA Type 4
R1 has a connected interface. (well, RFC says that the route should be intraarea or interarea. Does it mean that connected would not work?)
LSA type 4 is not necessary, because the ASBR/ABR (R2) and R1 are on the same area.
So, neither one is the cause of the problem on this scenario.
Cisco url http://www.cisco.com/warp/public/104/26.html also presents several reasons but none apply to this case.
If I configure R1 to run ospf on Vlan 200 interface, it installs the route 0.0.0.0:
router ospf 1
network (R2 Vlan 200 IP) 0.0.0.0 a x
passive vlan 200
I learned by practice that OSPF does not install the route if the local router has a local interface on the same Net of the Forward Address and OSPF is not running on this interface. But never found an official doc (Cisco, RFC) stating so.
Are you aware of docs explaining this case?
Here is the monitoring commands:
Route that is not installed on RIB:
#sh ip ospf database external 0.0.0.0
OSPF Router with ID (x.x.x.x) (Process ID 109)
Type-5 AS External Link States
LS age: 1367
Options: (No TOS-capability, DC)
LS Type: AS External Link
Link State ID: 0.0.0.0 (External Network Number )
Advertising Router: 100.4.254.237
LS Seq Number: 80000FD0
Checksum: 0xEBBF
Length: 36
Network Mask: /0
Metric Type: 1 (Comparable directly to link state metric)
TOS: 0
Metric: 1
Forward Address: 100.2.7.46
External Route Tag: 109
#sh ip route 0.0.0.0
% Network not in table
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