Exploring OSPF Messages Between New Neighbors
A basic network is setup and OSPF is configured. R1 is then prevented from forming an OSPF adjacency with R2 due to R1’s serial interface being configured as a passive interface.
Only Hello packets are seen from R2.
From this Wireshark output we can see:
- OSPF Version 2 is utilized
- This is a Hello packet
- The Hello packet is sourced from a router with OSPF Router ID 2.2.2.2. Duplicate RIDs will prevent an OSPF adjacency and cause other issues.
- The interface that sourced this Hello packet resides in OSPF area 0. This item is used to verify that the two connected router interfaces are within the same OSPF area – this is a requirement in order to form an OSPF adjacency.
- No authentication is used
- A /30 network mask is used on R2’s connected interface. This item is used to verify that the two connected router interfaces are using the same subnet mask, which is a requirement in order to form an OSPF adjacency in addition to the two interfaces being within the same primary subnet.
- Hello and Dead timers. These must be the same on both connected routers in order to Continue reading