[Xorp-users] Issues related to OSPF path selection
arvind
arvind at macil.in
Fri Jun 27 03:07:31 PDT 2008
A , B--> Server running router manager with 2 ethernet ports (With OSPF)
C------> Its a server running router manager with 10 ethernet ports(with
static and OSPF protocols)
This picture May not be clear in some systems for those I have explained
the setup below.
_________ _________ | | 172.16.3.1 172.16.3.2 | |
| A 1|<----------------------------->|1 B |
| 0 | | 0 | --------- --------- 172.16.2.1 ^
^ 172.16.1.1
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| _________ | | | | |
----------->| C |<-----------------
172.16.2.2 | | 172.16.1.2
---------
Server C has the following in configuration file:
protocols {
static {
disable: false
route 10.10.10.0/24 {
next-hop: 172.16.10.10
metric: 1
}
route 10.10.11.0/24 {
next-hop: 172.16.11.10
metric: 1
}
}
ospf4 {
router-id: 172.16.1.2
area 0.0.0.0 {
interface eth2 {
vif eth2.0 {
address 172.16.2.2 {
}
}
}
interface eth4 {
vif eth4.0 {
address 172.16.1.2 {
}
}
}
}
export: "connected,static"
}
}
policy {
policy-statement connected {
term export {
from {
protocol: "connected"
}
}
}
policy-statement static {
term export {
from {
protocol: "static"
}
}
}
}
interfaces {
restore-original-config-on-shutdown: true
interface eth0 {
disable: false
discard: false
description: "data interface"
mac: 00:bb:cc:dd:ee:00
mtu: 1500
vif eth0.0 {
disable: false
vlan {
vlan-id: 0
}
address 172.16.10.2 {
prefix-length: 24
broadcast: 172.16.10.255
disable: false
}
}
}
interface eth1 {
disable: false
discard: false
description: "data interface"
mac: 00:bb:cc:dd:ee:01
mtu: 1500
vif eth1.0 {
disable: false
vlan {
vlan-id: 0
}
address 172.16.11.2 {
prefix-length: 24
broadcast: 172.16.11.255
disable: false
}
}
}
interface eth2 {
disable: false
discard: false
description: "data interface"
mac: 00:bb:cc:dd:ee:02
mtu: 1500
vif eth2.0 {
disable: false
vlan {
vlan-id: 0
}
address 172.16.2.2 {
prefix-length: 24
broadcast: 172.16.2.255
disable: false
}
}
}
interface eth4 {
disable: false
discard: false
description: "data interface"
mac: 00:bb:cc:dd:ee:04
mtu: 1500
vif eth4.0 {
disable: false
vlan {
vlan-id: 0
}
address 172.16.1.2 {
prefix-length: 24
broadcast: 172.16.1.255
disable: false
}
}
}
}
I will explain the set-up (the Above diagram may not be clear while
receiving)
3 systems are there running with router manager A,B,C
A and B is connected with the network 172.16.3.1 nad 172.16.3.2
A and C is connected with the network 172.16.2.1 nad 172.16.2.2
B and C is connected with the network 172.16.1.1 nad 172.16.1.2
After running router manager in all the systems the OSPF states are
"full" and the "show route table ipv4 unicast ospf" is showing the
shortest path.But the issue is whenever the path is remove/broken (2 or
3 times) between any 2 systems and replacing then the back again it was
not showing the shortest path..
By giving "clear ospf database" the shortest paths are coming back again.
My Test:
I remove the path between A and C and replaced it back again but it was
not showing the shortest path.
Output checked in A:
output before removing the connection:
root at test1> show ospf4 neighbor
Address Interface State ID Pri
Dead
172.16.2.2 eth0/eth0 Full 172.16.1.2 128 30
172.16.3.2 eth1/eth1 Full 172.16.1.1 128 30
root at test1> show route table ipv4 unicast ospf
10.10.10.0/24 [ospf(110)/1]
> to 172.16.2.2 via eth0/eth0
10.10.11.0/24 [ospf(110)/1]
> to 172.16.2.2 via eth0/eth0
172.16.1.0/24 [ospf(110)/2]
> to 172.16.3.2 via eth1/eth1
172.16.10.0/24 [ospf(110)/1]
> to 172.16.2.2 via eth0/eth0
172.16.11.0/24 [ospf(110)/1]
> to 172.16.2.2 via eth0/eth0
root at test1>
output after removing the connection:
root at test1> show ospf4 neighbor
Address Interface State ID Pri
Dead
172.16.2.2 eth0/eth0 Down 172.16.1.2 0 0
172.16.3.2 eth1/eth1 Full 172.16.1.1 128 38
root at test1> show route table ipv4 unicast ospf
10.10.10.0/24 [ospf(110)/1]
> to 172.16.3.2 via eth1/eth1
10.10.11.0/24 [ospf(110)/1]
> to 172.16.3.2 via eth1/eth1
172.16.1.0/24 [ospf(110)/2]
> to 172.16.3.2 via eth1/eth1
172.16.10.0/24 [ospf(110)/1]
> to 172.16.3.2 via eth1/eth1
172.16.11.0/24 [ospf(110)/1]
> to 172.16.3.2 via eth1/eth1
root at test1>
Its fine still now, but the problem is after replacing the path between
A and C, It was not taking....
output after replacing the connection:
root at test1> show route table ipv4 unicast ospf
10.10.10.0/24 [ospf(110)/1]
> to 172.16.3.2 via eth1/eth1
10.10.11.0/24 [ospf(110)/1]
> to 172.16.3.2 via eth1/eth1
172.16.1.0/24 [ospf(110)/2]
> to 172.16.3.2 via eth1/eth1
172.16.10.0/24 [ospf(110)/1]
> to 172.16.3.2 via eth1/eth1
172.16.11.0/24 [ospf(110)/1]
> to 172.16.3.2 via eth1/eth1
root at test1>
If I give "clear ospf database" and then "show route table ipv4 unicast
ospf" then the paths are coming as shortest path.
At this situation If I remove the path between C and B,
System A doesnot know any route about the neighbors.
Can any one give the solution/idea for the above problem.
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