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Default Route Issue

danieltham
Level 1
Level 1

Hi,

I am experiencing a interesting problem with my default route on my router. As an example, I have a default route pointing to 192.168.1.254, i.e "ip route 0.0.0.0 0.0.0.0 192.168.1.254"

There are a few address that do not go to the default gateway automatically. However, if I put in their route "ip route 10.1.1.34 255.255.255.255 192.168.1.254" then they can be routed correctly. If I take them out, the traffic cannot be routed. However, address before and after it are ok, i.e 10.1.1.33 or 10.1.1.35 do not need to put a route to the gateway and they can be routed correctly but for 10.1.1.34, I must put in a static route to the gateway if not the traffic will just stop at the router.

Anyone know what could be the problem?

Daniel.

23 Replies 23

pkhatri
Level 11
Level 11

Hi Daniel,

Can you try applying the command 'ip classless' to your router and then checking if that makes it work. I suspect your router may be behaving in a classful fashion.

Paresh.

The ip classless command is already there. Actually the router has been running fine. Not sure when this started, it is only recently that we realise that we can't connect to some machines and after much trouble shooting, we found this issue. It took us a while to realise as we would expect any route not stated will go to the default route which did not happen for this case. Only after explicitly putting in the route then it can work. Very puzzled!

Thanks for your help anyway. Any other area I can look into?

Daniel

Hi Daniel,

I'm a bit confused!

Router has default route out of the network.OK

The Lan ip address for the router is what?

Is 10.1.1.34,34 and 35 client machines?

Where are you configuring the routes?

Sorry for the confusion, I am just using some ip as an example. Basically what is happening is that some of my router traffic is not going to the default route and only after explicitly putting in the route to point to the default gateway then they get routed correctly. If not the traffic just drop at the router. The router was working fine and this started only recently.

As to the .33 .34 and .35 thingy, I was trying to illustrate that the ip in concern here which can't be routed with a static route have neighbouring ip address working fine. It is just a few ip that is giving this problem. Meaning, if I can't route traffic to 10.1.1.34, I need to add a static route but for 10.1.1.33 and 10.1.1.35, they can be routed out without the static route as they use the default route. The ips are all on the same network.

Hope that clear the confusion. Thanks!

Daniel

Thanks for clearing that up. Yep, does sound odd.

Can you try an extended ping and traceroute from the router for the affected address without the host route configured.

You can do the extended ping by typing "ping" and follow the options. Change the source addess to the affected address 10.1.1.34.

Cheers

Sarb

From a PC when I ping to the affected addresses, if the static route is not added, I will get time out but if I put in the static route, it will be ok. When I do a trace from the PC to the affected addresses, if the static route is not added, the trace will reach the router and die from there on. If I put in the static route, it will go to the next hop which is a firewall and from there reach its destination.

Could it be a hardware issue??

Daniel

Hi Daniel,

Please check the route for the particular IP/Subnet which you are pointing to.

For eg.

sh ip route 10.1.1.34

There may be a static or dynamically learnt route for that particular IP/subnet. This may be causing the problem for you. Request you to post the output of show ip route command incase if this does not work.

Rgds,

Naveen B

Ok, forget about the 10.1.1.34 ip. Here is the route entries on the router

ip classless

ip route 0.0.0.0 0.0.0.0 10.1.20.21

ip route 192.168.77.197 255.255.255.255 10.1.22.250

ip route 192.168.77.198 255.255.255.255 10.1.22.250

ip route 192.168.77.246 255.255.255.255 10.1.20.21

ip route 192.168.75.134 255.255.255.255 10.1.22.250

ip route 192.168.173.99 255.255.255.255 10.1.20.21

ip route 192.168.173.118 255.255.255.255 10.1.22.250

ip route 205.183.246.0 255.255.255.0 10.1.9.253

ip route 206.190.105.208 255.255.255.255 10.1.1.148

ip route 206.190.105.210 255.255.255.255 10.1.1.148

ip route 208.134.161.0 255.255.255.0 10.1.9.253

If you notice, there are 2 routes that points to the default gateway, 192.168.77.246 and 192.168.173.99 . These are the problem ip. There is another one that I have removed to show the sh ip route. See below

sh ip route 192.168.77.193

% Subnet not in table

LAN_Router2#sh ip route 192.168.77.193 255.255.255.255 longer-prefixes

Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP

D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP

i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area

* - candidate default, U - per-user static route, o - ODR

P - periodic downloaded static route

Gateway of last resort is 10.1.20.21 to network 0.0.0.0

LAN_Router2#sh ip route 192.168.77.193 255.255.255.0 longer-prefixes

Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP

D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP

i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area

* - candidate default, U - per-user static route, o - ODR

P - periodic downloaded static route

Gateway of last resort is 10.1.20.21 to network 0.0.0.0

192.168.77.0/32 is subnetted, 3 subnets

S 192.168.77.246 [1/0] via 10.1.20.21

S 192.168.77.198 [1/0] via 10.1.22.250

S 192.168.77.197 [1/0] via 10.1.22.250

LAN_Router2#

Presently I cannot connect to 192.168.77.193 but 192.168.77.246 is ok with the static route in.

Thanks!

Daniel

Hi,

Is 10.1.20.21 a Nortel device???

-Sai.

It is a CheckPoint Firewall on a Sun server. On NGX R60. Is this an issue with the Firewall?

dan

It is a CheckPoint Firewall on a Sun server. On NGX R60. Is this an issue with the Firewall?

dan

It is a CheckPoint Firewall on a Sun server. On NGX R60. Is this an issue with the Firewall?

dan

I would be curious to hear the outcome of this problem. I am having a similar one where I have a static network route (for example 10.x.x.x/16) pointing to a next hop that is a Checkpoint firewall and on occasion I get hosts within that /16 that require host routes pinting to the same next hop because they don't get routed via the /16 route. Tried an IOS upgrade without success. Using workaround keyword permanent on the host routes so they always work. Sounds like this could be a similar situation.

Hi,

If you look at FW logs, do you see the packets for IPs that you assume router is dropping? This would verify which device drops the packets, router or FireWall.

David

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