Subnet to Internet connection routing

[Brian Taylor]

We have 2901 on version 15.5(3)M3. The router has multiple internet connections and subnets each on their own VLAN.

Currently I use PBR to direct traffic between different subnets and their associated internet connection. There is also a

default route

(example below).

This seems to work in that

what's my ip address

returns the correct public IP address for the assigned internet connection.

However I notice that when I do a

trace route (say to 8.8.8.8)

on any of the internet connections, either on the router or a computer, they always show the

default route

(i.e. it is identical for every internet connection).

So I'm confused. Where should I start looking to investigate this?

Brian

ip route 0.0.0.0 0.0.0.0 Dialer6
access-list 181 permit ip any 192.168.0.0 0.0.0.255
route-map GIG4 permit 10
 match ip address 181
 set ip next-hop <ip address> or other times set interface Dialer5
interface GigabitEthernet0/1.4
 ip policy route-map GIG4
ip nat inside source list 170 interface gig0/0.70 overload
access-list 170 permit ip 192.168.0.0 0.0.0.255 any

[guruvignesh]

Hello Brian,

you're using Policy-Based Routing (PBR) to direct traffic between different subnets and their associated internet connections. The

default route

is set to Dialer6 for outgoing traffic. However, when you perform a

trace route to 8.8.8.8,

the trace shows the

default route

for all internet connections.

To investigate, start by confirming the configuration of your PBR rules. Ensure that the

route-map GIG4

is correctly matching the desired traffic based on your access list 181. Double-check the next-hop or interface specified in the

route-map.

Additionally, verify the

NAT configuration (ip nat inside source)

to confirm that

NAT

is properly translating internal IP addresses to the correct public IP associated with each internet connection.

Lastly, check the routing table

(show ip route)

to ensure that the PBR is indeed correctly routing the traffic based on your defined rules and that there are no conflicting routes causing the

trace route

to consistently show the

default route.

[MHM Cisco World]

I dont get it 

Can you share config 

[Brian Taylor]

Thanks for the responses! The configuration is quite long so I've stripped out the irrelevant details and also color coded the various subnet and internet interfaces - I hope this helps, see the attached file (now deleted).

[Brian Taylor · Accepted solution]

Ok I managed to fix the problem. I deleted the

default route(no ip route 0.0.0.0 0.0.0.0 Dialer6)

and then added the following on each subnet (defining RM1, RM2, RM3 etc):

route-map RM1 permit 10
 set default interface <outside internet interface> OR set ip default next-hop <outside internet gateway>
interface <internal subnet interface>
 ip policy route-map RM1

The existing

 ip nat

inside source were fine, providing

nat

from the subnet to the internet interface

[paul driver]

Hello
Good to hear you have a solution, however in your OP it suggests you do not have resiliency, meaning if one of those internet connections fail, then the traffic for that particular

RM/NAT

will be policy routed into a black hole, I believe you will require some IPSLA boolean tracking to accommodate any upstream ISP failure.

in this instance can elaborate on what how you would like your traffic to be re-routed ( o which remaining active ISP interface)

[Brian Taylor]

Thanks Paul, I've started to have a look at IP SLA features in the router.