Route-map Cisco IOS

Policy-Based Routing or PBR with Cisco IOS.

Introduction

Route-maps are often used with Routing Protocols such as BGP and use Prefix-lists

Enabling PBR on 3560 Switch platform

On the 3560 Switch platform you get the message %PLATFORM_PBR-4-SDM_MISMATCH: PBR requires sdm template routing when you apply a route-map to a Interface.

• Remember: Use terminal monitor if you are not on the console to receive messages from the console.

This is because the SDM (Switch Database Management) template. The SDM manages the layer 2 and layer 3 switching information that is maintained in the Ternary Content Addressable Memory (TCAM). The TCAM is used for forwarding lookups. See . There are some unsupported commands on IOS 12.2-25

CEF uses default Source/Destination load sharing, ensuring same path for the packetstreams.

Looking at the default configuration the switch had the following SDM configuration.

Core2#<input>sh sdm prefer</input>
 The current template is "desktop default" template.
 The selected template optimizes the resources in
 the switch to support this level of features for
 8 routed interfaces and 1024 VLANs.

  number of unicast mac addresses:                  6K
  number of IPv4 IGMP groups + multicast routes:    1K
  number of IPv4 unicast routes:                    8K
    number of directly-connected IPv4 hosts:        6K
    number of indirect IPv4 routes:                 2K
  number of IPv4 policy based routing aces:         <notice>0</notice>
  number of IPv4/MAC qos aces:                      512
  number of IPv4/MAC security aces:                 1K

Changing SDM Bias

Core2(config)#<input>sdm prefer routing</input>
Changes to the running SDM preferences have been stored, but cannot take effect
until the next reload.
Use 'show sdm prefer' to see what SDM preference is currently active.
Core2(config)#<input>^Z</input>
Core2#
1d00h: %SYS-5-CONFIG_I: Configured from console by vty0 (10.0.0.30)
Core2#<input>reload</input>

After reboot

Core2#<input>sh sdm prefer</input>
 The current template is "desktop routing" template.
 The selected template optimizes the resources in
 the switch to support this level of features for
 8 routed interfaces and 1024 VLANs.

  number of unicast mac addresses:                  3K
  number of IPv4 IGMP groups + multicast routes:    1K
  number of IPv4 unicast routes:                    11K
    number of directly-connected IPv4 hosts:        3K
    number of indirect IPv4 routes:                 8K
  number of IPv4 policy based routing aces:         <notice>512</notice>
  number of IPv4/MAC qos aces:                      512
  number of IPv4/MAC security aces:                 1K

Example

Lots of limitations on 3560 platform. Default route to 192.168.1.0/24 to 10.0.0.30 gateway all other to 10.0.0.34 gateway

ip access-list extended ISP-CON1
 remark Internally used nets denied. They should be routed by the FIB
 deny   ip 192.168.1.0 0.0.0.255 10.0.0.0 0.255.255.255
 deny   ip 192.168.1.0 0.0.0.255 192.168.0.0 0.127.255.255
 permit ip 192.168.1.0 0.0.0.255 any
!
ip prefix-list DEFAULT seq 5 permit 0.0.0.0/0
!
route-map HETH permit 5
 match ip address ISP-CON1
 set ip next-hop 10.0.0.30
!
route-map HETH permit 10
 match ip address prefix-list DEFAULT
 set ip next-hop 10.0.0.34

Testing

Easy way of testing is using extended traceroute.

traceroute ip
172.16.4.16
192.168.1.1
y

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Links

• Cisco Policy-Based Routing Using the set ip default next-hop and set ip next-hop Commands Configuration Example
• Cisco Understanding Policy Routing