Huawei Quidway NetEngine80E Configuration Manual page 289

HUAWEI NetEngine80E/40E Router
Configuration Guide - IP Routing
Smart-discover
Generally, routers periodically send Hello packets through interfaces that run OSPF, routers set
up and maintain the neighbor relationship, and elect the DR and the Backup Designated Router
(BDR) on the multi-access network (broadcast or NBMA) by exchanging Hello packets. When
establishing the neighbor relationship or electing the DR and the BDR on the multi-access
network, interfaces can send Hello packets only when the Hello timer expires. This affects the
speed for establishing the neighbor relationship and electing the DR and the BDR.
The Smart-discover function can solve the preceding problem.
l
l
Local MT
When multicast and a MultiProtocol Label Switching (MPLS) Traffic Engineering (TE) tunnel
are deployed in a network simultaneously, services become unavailable because the multicast
function may be affected by the TE tunnel. This is because after the TE tunnel is enabled with
IGP Shortcut, the outgoing interface of the route calculated by IGP is not the actual physical
interface but a TE tunnel interface. According to the unicast route to the multicast source address,
a router sends a Join message through a TE tunnel interface. Routers spanned by the TE tunnel
cannot sense the Join message, and therefore multicast forwarding entries cannot be created.
The TE tunnel is unidirectional, so multicast data packets sent by the multicast source are sent
to the routers spanned by the TE tunnel through related physical interfaces. The routers, however,
do not have multicast forwarding entries. As a result, the multicast data packets are discarded.
Services therefore become unavailable.
Issue 02 (2014-09-30)
NOTE
l The interval for sending Hello packets on an interface depends on the interval for sending Hello packets
set on the interface.
l The default value of the interval for sending Hello packets varies with the network type.
In broadcast and NBMA networks, the neighbor relationship can be established rapidly and
a DR and a BDR on the networks can be elected rapidly.
When the neighbor status becomes 2-way for the first time, or it returns to Init from the 2-
way or higher state as shown in
function sends Hello packets to the neighbor without waiting for the timeout of the Hello
timer when the interface finds that the status of the neighbor changes.
When the interface status of the DR and the BDR in the multi-access network changes, the
interface enabled with the Smart-discover function sends Hello packets to the network
segment and takes part in the DR or BDR election.
Figure 5-3 Changes of the neighbor state machine
Down Init
Attempt
(NBMA)
On P2P and P2MP networks, the adjacency relationship can be established rapidly. The
principle is the same as that in broadcast and NBMA networks.
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Figure 5-3, the interface enabled with the Smart-discover
2-way Exstart
5 OSPF Configuration
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