OSPF ROUTING ISSUE

maninder_singh.negi1 · ‎10-14-2015

Hello Experts ,

I will be grateful if someone can help me in knowing what is happening wrong with my set up .

Topology is simple :

R1 -------R 2

| |

Riverbed

| |

SW ------- |

Between R1 and Switch ,One device riverbed is connected .

R2 is directly connected to Switch

There is IBGP between R1 and R2 through Switch.

OSPF is running between Switch and Router R1 and R2

R1

router ospf 65000
router-id 1.1.1.1
log-adjacency-changes
area 0 authentication message-digest
passive-interface default
no passive-interface FastEthernet0/1
network 1.1.1.1 0.0.0.0 area 0
default-information originate metric 1

!
interface FastEthernet0/1
ip address 1.1.1.1 255.255.255.224

ip route 0.0.0.0 0.0.0.0 FastEthernet0/0 2.2.2.1 30

R2

router ospf 65000
router-id 1.1.1.2
log-adjacency-changes
area 0 authentication message-digest
passive-interface default
no passive-interface FastEthernet0/0
network 1.1.1.2 0.0.0.0 area 0
default-information originate metric 100

!
interface FastEthernet0/0
ip address 1.1.1.2 255.255.255.224

ip route 0.0.0.0 0.0.0.0 MFR2.1 3.3.3.1 230

Switch configuration is not with me .

Objective of configuration to make sure traffic from Switch should come R1 but strange thing is happening that Traffic is coming

to both R1 and R2 , Can someone explain why this strange thing is happening ???

Morne Vermeulen · ‎10-14-2015

Hi,

From what I have read (and I might be on the completely wrong path here...) it seems that there is a problem with the route selection between both the IBGP and OSPF sessions. It seems that traffic is taking any path that is selected first, rather than falling back onto metrics and such.

Have you tried distributing the OSPF session into the IBGP session? I think if the two routing protocols know of each other this might not happen.

Still new to networking, I might be approaching this the wrong way.

Hope this helps!

Regards, Morne

maninder_singh.negi1 · ‎10-14-2015

Apologies I overlook the configuration.

Traffic is coming over back up path between SW and R2 even though configuration is in place to make SW to forward traffic to R1

No redistribution of OSPS routes into BGP.

R1 is not generating any LSA5

R1#sh ip ospf database

Type-5 AS External Link States

Link ID ADV Router Age Seq# Checksum Tag
0.0.0.0 1.1.1.2 830 0x8000059E 0x00734A 65000

R2#sh ip ospf database
Type-5 AS External Link States

Link ID ADV Router Age Seq# Checksum Tag
0.0.0.0 1.1.1.2 922 0x8000059E 0x00734A 65000

SW#sh ip ospf database

Type-5 AS External Link States

Link ID ADV Router Age Seq# Checksum Tag
0.0.0.0 1.1.1.2 1009 0x8000059E 0x00734A 65000

Below is Switch configuration

router ospf 1
router-id 1.1.1.3
log-adjacency-changes detail
nsf cisco enforce global
area 0 authentication message-digest
redistribute connected metric 100 metric-type 1 subnets
passive-interface default
no passive-interface Vlan1
network 0.0.0.0 255.255.255.255 area 0

Morne Vermeulen · ‎10-14-2015

Hi Mahinder,

It still sounds like the metrics are incorrect. Have you tried manually changing the route metric from SW to R1 so that you know that is the preferred route instead of the backup link running to R2?

maninder_singh.negi1 · ‎10-15-2015

Hello ,

We cannot make any changes on Switch all changes we can do only on router

When R1 is sending default route with metric 1 then why that route is not getting

preferred and most important why R1 is not generating any LSA 5 for Default route.

R1 #sh ip ospf database

OSPF Router with ID (1.1.1.1) (Process ID 65000)

Router Link States (Area 0)

Link ID         ADV Router      Age         Seq#       Checksum Link count
1.1.1.3            1.1.1.3    1559        0x800022BF 0x008113 4
1.1.1.1            1.1.1.1    398         0x800022E3 0x00A666 1
1.1.1.2            1.1.1.2    344         0x800022C5 0x00E047 1

Net Link States (Area 0)

Link ID ADV Router Age Seq# Checksum
1.1.1.3 1.1.1.3 1559 0x800013EF 0x001419

Type-5 AS External Link States

Link ID ADV Router Age Seq# Checksum Tag
0.0.0.0 1.1.1.2 344 0x800005C3 0x00296F 65000

R1#sh ip route ospf
O*E2 0.0.0.0/0 [110/100] via 1.1.1.2, 4w6d, FastEthernet0/1

==========================================================================================

R2#sh ip ospf database

OSPF Router with ID (1.1.1.2) (Process ID 65000)

Router Link States (Area 0)

Link ID         ADV Router      Age         Seq#       Checksum Link count
1.1.1.3    1.1.1.3    1957        0x800022BF 0x008113 4
1.1.1.1    1.1.1.1    796         0x800022E3 0x00A666 1
1.1.1.2    1.1.1.2    740         0x800022C5 0x00E047 1

Net Link States (Area 0)

Link ID ADV Router Age Seq# Checksum
1.1.1.3 1.1.1.3 1957 0x800013EF 0x001419

Type-5 AS External Link States

Link ID ADV Router Age Seq# Checksum Tag
0.0.0.0 1.1.1.2 740 0x800005C3 0x00296F 65000

R2#sh ip route ospf
57.0.0.0/8 is variably subnetted, 392 subnets, 12 masks
O 57.28.35.128/25 [110/2] via 1.1.1.3, 4w6d, FastEthernet0/0

maninder_singh.negi1 · ‎10-15-2015

Hello Vermeulen ,

I checked and found in R1 even though below static is configured below route is not best in routing table so first thing need to check is that why below static route is not

best in routing table .

Can you shed some light on this

ip route 0.0.0.0 0.0.0.0 FastEthernet0/0 57.213.18.161 30

R1#sh ip route 0.0.0.0
Routing entry for 0.0.0.0/0, supernet
Known via "ospf 65000", distance 110, metric 100, candidate default path
Tag 65000, type extern 2, forward metric 1
Last update from 1.1.1.2 on FastEthernet0/1, 4w6d ago
Routing Descriptor Blocks:
* 1.1.1.2, from 1.1.1.2, 4w6d ago, via FastEthernet0/1
Route metric is 100, traffic share count is 1
Route tag 65000

Rolf Fischer · ‎10-15-2015

Hi,

could you share the output of

- show ip interface brief Fa0/0

and

- show ip cef 57.213.18.161

The numeric next-hop (57.213.18.161) has to be reachable through interface Fa0/0 in order to install the static default-route (with an AD of 30).

HTH

Rolf

maninder_singh.negi1 · ‎10-15-2015

Hello Rolf ,

Below are logs but I saw another set up and in that configuration static route is

defined with next hop interface as serial instead of fast Ethernet and everything seem working fine whether it can be any issue related to interface type ??

R1#sh ip int brief
Interface                  IP-Address      OK? Method Status                Protocol
FastEthernet0/0            unassigned      YES manual up                    up
FastEthernet0/0.3          unassigned      YES manual deleted               down
FastEthernet0/0.728        57.213.18.162   YES manual up                    up

R1#sh ip cef 57.213.18.161
57.213.18.161/32, version 2624, epoch 0, connected, cached adjacency 57.213.18.161
0 packets, 0 bytes
Flow: Origin AS 0, Peer AS 0, mask 30
via 57.213.18.161, FastEthernet0/0.728, 644 dependencies
next hop 57.213.18.161, FastEthernet0/0.728
valid cached adjacency

Rolf Fischer · ‎10-15-2015

I'd need to do some testing first but I believe you'll need to replace the main-interface (Fa0/0) with the subinterface (Fa0/0.728) in your static route configuration:

ip route 0.0.0.0 0.0.0.0 FastEthernet0/0.728 57.213.18.161 30

From what I see, I'm not sure if it is necesary (or makes sense) to bind the next-hop resolution to a particular interface in your setup.

HTH

Rolf

Rolf Fischer · ‎10-17-2015

Confirmed. It has to be the subinterface

R1(config)#do show ip int brief
Interface                  IP-Address      OK? Method Status                Protocol
FastEthernet0/0            unassigned      YES unset  up                    up
FastEthernet0/0.728        57.213.18.161   YES manual up                    up

R1(config)#ip route 0.0.0.0 0.0.0.0 Fa0/0 57.213.18.161 30
R1(config)#do show ip route static
! <no output>
R1(config)#no ip route 0.0.0.0 0.0.0.0 Fa0/0 57.213.18.161 30
R1(config)#ip route 0.0.0.0 0.0.0.0 Fa0/0.728 57.213.18.161 30
R1(config)#do show ip route static
S*   0.0.0.0/0 [30/0] via 57.213.18.161, FastEthernet0/0.728

The configuration of an exit-interface in a static route entry with a numerical next-hop (IP address) is optional. As the example above indicates, the numeric next-hop has to be reachable through the configured IP interface, otherwise the route won't come up. Without the configuration of the exit-interface the default-route would come up (even with Fa0/0 disabled) if another route for the next-hop IP exists. This could be a summary route learnd from another router or a local discard route e.g.

ip route 57.213.0.0 255.255.0.0 null 0

As mentioned in my previous post, based on the information provided so far I don't know if it is necesary do define the exit-interface in this case.

HTH

Rolf

Morne Vermeulen · ‎10-14-2015

Try this, send me the output from "show ip route" on all three devices?

Lets check if there is something weird with Admin Distance or metric. Then we can determine why the secondary link is preferred.