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Knowledge Base

FAQ-Routing Policy on the Router Fails to Take Effect Because the Next Hop Type for Redirection Is Incorrect

Publication Date:  2012-07-27  |   Views:  3  |   Downloads:  0  |   Author:  y24772  |   Document ID:  EKB0000337037

Contents

Issue Description

 Q:
The customer requires the packets in the inbound direction of AR2811 interface Tunnel1 to be redirected to a server attached to interface Ethernet0/0. The relevant configurations are as follows:
acl number 2000
rule 100 permit
route-policy a1 permit node 5
if-match acl 2000
apply output-interface Ethernet 0/0
interface Tunnel1
ip address 10.1.1.1 255.255.255.128
ip policy route-policy a1
source Ethernet0/1
destination 124.74.x.x
After the previous configurations, the server attached to Ethernet0/0 fails to receive the redirected packets. 

 

Alarm Information

 Null 

Handling Process

 A:
Modify the configurations as follows:
route-policy a1 permit node 5
if-match acl 2000
apply ip-address next-hop 202.101.x.x (IP address of the server)
Perform the test again and packets can be successfully redirected. 

 

Root Cause

 View the count of the route-policy. There are matched packets, but the number of packets going out of interface Ethernet 0/0 does not increase. In accordance with the packet forwarding principle, the device advertises packets according to the routing table, determines the outbound interfaces, encapsulates the MAC addresses of the next hop IP addresses into the packets, puts the packets in a queue, and forwards them. The device, however, does not know the next hop of the packets redirected to the interface. Therefore, the device is unable to encapsulate and forward them.
If the packets are redirected to the next hop IP address, they can be encapsulated and forwarded. 
 

Suggestions

 In a broadcast network such as an Ethernet, the next hop IP address must be specified for redirection. In a P2P network such as a PPP network, the next hop interface can be specified for redirection.