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Knowledge Base

R2630: Two PCs in the Same Network Segment Cannot Interwork Due To No ARP Proxy Configuration

Publication Date:  2012-07-27  |   Views:  507  |   Downloads:  0  |   Author:  chenshunquan  |   Document ID:  EKB0000008651


Issue Description

Networking: PC 1----Ethernet 1----2630 router 1---WAN-----2630 router 2---Ethernet 2-----PC 2 Ethernet 1 and Ethernet 2 belong to the same network segment, and pinging PC 2 from PC 1 fails.

Alarm Information


Handling Process

There are two methods: 1) Make the router deal with the packets of the local network segment that are sent from the downlink network segment, that is, enable the ARP proxy function and configure host route. Add a host route from 2630 router 1 to PC 2 and a host route from 2630 router 2 to PC 1. Enable the ARP proxy for the two Ethernet ports using the IP Proxy-ARP command. This measure is of course applicable to the case where there are a small number of PCs. 2) Define two subnets, that is, classify the two Ethernet segments to two subnets (through mask). Suppose Ethernet network segment 1 is classified to subnet 1, and Ethernet network segment to subnet 2. Configure a network segment route from 2630 router 1 to subnet 2 and also such a route from 2630 router 2 to subnet 1.

Root Cause

The routing table of 2630 router 1 contains a direct route of an Ethernet network segment (automatically created) with an Ethernet port as the next hop. So does 2630 router 2. In this case, when PC 1 sends an ARP packet to the router, the router will discard it as it belongs to the local Ethernet network segment, thus disabling PC 1 to send packets to PC 2.