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Monday, October 18, 2010

Question 143

How do you ensure that  packets sourced from 192.168.1.1 uses serial 1/0 as the default route and packets sourced from 192.168.1.2 uses serial 1/1 as its default route? Note: the default route should only be use when there is not a more explicit route in the routing table. 
Posted by Packets Analyzed at 7:14 PM
Labels: ,

2 comments:

networkdongle said...

another good one, wish i could remember these things and not have to keep looking them up, but i guess if i can find them on the doccd doing ok also...


Policy-based routing:

set ip default next-hop ip-address [ip-address]

Specifies the next hop to which to route the packet, if there is no explicit route for this destination.

Note Like the set ip next-hop command, the set ip default next-hop command must specify an adjacent router.

set default interface interface-type interface-number [... interface-type interface-number]


Specifies the output interface for the packet if there is no explicit route for the destination.

http://www.cisco.com/en/US/customer/docs/ios/iproute_pi/configuration/guide/iri_ip_prot_indep_ps6441_TSD_Products_Configuration_Guide_Chapter.html#wp1056703

October 22, 2010 at 11:33 AM
Packets Analyzed said...

I did an example up for "set default interface" but you can use "set ip default next-hop" as well.

Note: I have another router that has an IP address of 10.255.255.1 for pinging purposes.

R6
__

do sh run | sec route-map
ip policy route-map DEFAULT_ROUTE
ip local policy route-map DEFAULT_ROUTE
route-map 1 permit 10
route-map DEFAULT_ROUTE permit 10
match ip address 10
set default interface Serial1/0
route-map DEFAULT_ROUTE permit 20
match ip address 20
set default interface Serial1/1

access-list 10 permit 192.168.1.1
access-list 20 permit 192.168.1.2

interface Serial1/2
description Serial-R7
ip address 192.1.1.100 255.255.255.0
ip policy route-map DEFAULT_ROUTE
serial restart-delay 0

interface Serial1/0
description Serial-R5-Con1
ip address 10.0.0.1 255.255.255.0

interface Serial1/1
description Serial-R5-Con2
ip address 10.0.1.1 255.255.255.0

R7
__

interface Serial1/0
description - Serial-R6
ip address 192.1.1.2 255.255.255.0 secondary
ip address 192.1.1.1 255.255.255.0
serial restart-delay 0
no fair-queue

interface FastEthernet0/0
ip address 192.168.1.2 255.255.255.0 secondary
ip address 192.168.1.1 255.255.255.0

Ping from both 192.168.1.1/2

R7
__

debug ip policy

*Mar 1 04:24:25.998: IP: s=192.168.1.1 (Serial1/2), d=10.255.255.1 (Serial1/0), len 100, FIB policy routed

*Mar 1 04:25:22.738: IP: s=192.168.1.2 (Serial1/2), d=10.255.255.1 (Serial1/1), len 100, FIB policy routed

October 23, 2010 at 5:13 PM

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