RE: Policy Based Routing Question "set interface Loopback0"

From: ismail el-shalh (ishelh_mdsa@yahoo.com)
Date: Fri Aug 11 2006 - 00:19:40 ART


  Debug ip policy and debug ip packet detail
   
  ON R2
   
  IP: s=172.16.0.2 (local), d=204.12.1.3, len 100, policy match
  IP: route map POLICY, item 10, permit
   
  IP: s=172.16.0.2 (local), d=204.12.1.3 (Loopback0), len 100, policy routed
                                                         |
                                                         |
                                                        \|/
  IP: local to Loopback0 204.12.1.3 <----- 204.12.1.3 is not a loopback but why the debug is showing it as loopback?
   
                                                                  
   
   
   ON R2
   
  Rack1R2#ping 204.12.1.3 source 172.16.0.2 repeat 1
   
   
                                             -> Why 172.16.0.2 is showing as Loopback0 ?
                                             |
  IP: tableid=0, s=172.16.0.2 (Loopback0), d=204.12.1.3 (Ethernet0), routed via RIB
   
   
  IP: s=167.1.27.100 (Loopback0), d=204.12.1.3 (Ethernet0), g=167.1.27.7, len 100, forward
      ICMP type=8, code=0
   
   
  IP: tableid=0, s=204.12.1.3 (Ethernet0), d=172.16.0.2 (Ethernet0), routed via RIB
  IP: s=204.12.1.3 (Ethernet0), d=172.16.0.2 (Ethernet0), len 100, rcvd 3
      ICMP type=0, code=0
  
 
  I will be grateful if someone can explain this to me.
   
  Thanks in advance
    
ismail el-shalh <ishelh_mdsa@yahoo.com> wrote:

  Hi Brian,

Thanks for the clarification But still I am not able to get the concept of why we usually set the output to a loopback interface!

for example in LAB 14, Task 11.1 (NAT on a Stick) you used this command in your solution.

R2

interface loopback 0
ip nat inside

inter fas0/0
ip addd 172.16.0.2 255.255.255.0 secondary
ip address 167.1.27.2 255.255.255.0
ip nat outside
ip policy route-map POLICY

ip nat pool INSIDE_GLOBAL 167.1.27.100 167.1.27.199 netmask 255.255.255.0
ip nat inside source list INSIDE_LOCAL pool INSIDE_GLOBAL

ip access-list standard INSIDE_LOCAL
permit 172.16.0.0 0.0.0.255
!
!
route-map POLICY permit 10
match ip address INSIDE_LOCAL
set interface Loopback0 <------------- How this command is helping here?

Brian Dennis wrote:
From the DocCD:

set interface
To indicate where to output packets that pass a match clause of a route
map for policy routing, use the set interface command in route-map
configuration mode. To delete an entry, use the no form of this command.

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

http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/
fiprrp_r/ind_r/1rfindp2.htm#wp1020570

HTH,

Brian Dennis, CCIE #2210 (R&S/ISP-Dial/Security)
bdennis@internetworkexpert.com

Internetwork Expert, Inc.
http://www.InternetworkExpert.com
Toll Free: 877-224-8987
Direct: 775-745-6404 (Outside the US and Canada)

-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
ismail el-shalh
Sent: Thursday, August 10, 2006 5:15 PM
To: ccielab
Subject: Policy Based Routing Question "set interface Loopback0"

Dear Group, what does "set interface Loopback0" means in the following
configuration :

interface FastEthernet0/0
ip address 167.1.5.5 255.255.255.0
ip policy route-map POLICY

access-list 30 permit 167.1.5.0 0.0.0.255

interface loopback 0
ip address 150.1.5.5 255.255.255.0

route-map POLICY permit 10
match ip address 30
set interface Loopback0

Thanks,
Ismail

---------------------------------
Do you Yahoo!?
Next-gen email? Have it all with the all-new Yahoo! Mail Beta.



This archive was generated by hypermail 2.1.4 : Fri Sep 01 2006 - 15:41:56 ART