Both MA5200G are connected by running OSPF at ATM. To speed up the network convergence, the carrier should set the default NBMA of ATM interface to P2P (without election of DR and BDR). However, OSPF services do not communicate after the modification.
Enter the following command in the PVC mode of ATM interface:
map ip X.X.X.X //the former version needs to add one brostcast parameter, and the new version is configured with the parameter by default.
The command can make ATM interface generate a pseudo-multicast, so the multicast packets of OSPF can be forwarded.
1. The network type of devices at both sides connected through the ATM interface is set to P2P.
2. According to checkup, the state of OSPF of both devices is DOWN.
3. Open the OSPF debugging switch, and only hello packets transmitted can be found, without hello packets received.
4. It is suspicious the links are problematic, but the problem persists after replacing the links.
5. Deploy a hub between two devices to capture packets, and no hello packet is found over the links.
After the analysis above, it is found that ATM interface does not transmit OSPF packets out. Specifically, the type of ATM interface is defaulted to NBMA in OSPF. After the neighbor is configured, ATM interface will unicast route information to the peer. When the network type of ATM interface is set to P2P, ATM interface cannot forward the multicast and broadcast packets of OSPF (it depends on the feature of ATM). As a result, the links have not hello packets, and no neighbor can be set up.