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| 6.2 |  | Implementing Router Redundancy in a Switched Network |
| 6.2.6 |  | Single Router Mode (SRM) redundancy |

SRM redundancy is another alternative to having both MSFCs in a chassis active at the same time.

Using SRM redundancy, only the designated router MSFC is visible to the network at any given time. The non-designated router is booted up completely and participates in configuration synchronization, which is automatically enabled when entering SRM. Unlike the MSFC high availability method, the configuration of the non-designated router is exactly the same as the designated router, but its interfaces are kept in a "line down" state and are not visible to the network. Processes, such as routing protocols, are created on the non-designated router and the designated router. All non-designated router interfaces are in a "line down" state and do not send or receive updates from the network.

When the designated router fails, the non-designated router changes its state to become the designated router and the interface states change to "link up". The router builds its routing table while the existing Supervisor engine switch processor entries are used to forward Layer 3 traffic. After the newly designated router builds its routing table, the entries in the switch processor are updated.