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Knowledge Base

Network failure due to EIGRP on Cisco Router

Publication Date:  2013-06-23  |   Views:  994  |   Downloads:  0  |   Author:  SU1000965009  |   Document ID:  EKB1000030353


Issue Description

Topology: Regional C7206--Provincial NE40--C6509--C7513
                 |                       |                     |                 |
               Regional NE20--Provincial NE40--C6509--C7507
Description: CISCO equipment runs EIGRP, and the network is added a new product from Huawei. For a smooth cutover of network, CISCO equipment is configured with EIGRP and OSPF simultaneously, and enable the same network segment in EIGRP and OSPF so that both routing protocols could learn the same route. The priority of EIGRP is higher than that of OSPF, so the configuration of OSPF will not influence the normal running of network. When the network runs well, change the priority of EIGRP, and CISCO equipment is switched to OSPF first; at this point, if no problem occurs, the configuration of EIGRP could be deleted then, without any impact on current network. However, problem occurs to network many times after CISCO equipment is configured with two routing protocols, and partial routes cannot be learned. Network crashes, and the network sentence in EIGRP is lost. 

Alarm Information


Handling Process

Smooth cutover cannot come to truth because of the problem on CISCO equipment. Before configuring of OSPF for expansion of network, delete the EIGRP configuration on CISCO equipment. 

Root Cause

After consultation, it is found that problem will occur once the same network segment is enabled in both EIGRP and OSPF if CISCO equipment runs two. So it is not recommended to configure like this. However, both protocols could co-exist, and they could be imported mutually. 


Huawei products could communicate with the counterpart from CISCO through both ISIS and OSPF. It is feasible to enable the same network segment in two protocols. However, it is conditioned for CISCO equipment to use both EIGRP and OSPF, and problem may occur to network if the same network segment is enabled in two protocols. In my opinion, because both ISIS and OSPF are based on link state database and SPF; unlike OSPF, however, EIGRP uses DUAL, resulting in problem in co-existence of two protocols.