Extreme Networks ExtremeWare 7.2e, Инструкция по установке и эксплуатации

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234 ExtremeWare 7.2e Installation and User Guide
Interior Gateway Protocols
Triggered Updates
Triggered updates occur whenever a router changes the metric for a route, and it is required to send an
update message immediately, even if it is not yet time for a regular update message to be sent. This will
generally result in faster convergence, but may also result in more RIP-related traffic.
To enable triggered updates on RIP, issue this command:
enable rip triggerupdate
To disable triggered updates on RIP, issue this command:
disable rip triggerupdate
Route Advertisement of VLANs
VLANs that are configured with an IP address, but are configured to not route IP or are not configured
to run RIP, do not have their subnets advertised by RIP. Only those VLANs that are configured with an
IP address and are configured to route IP and run RIP have their subnets advertised.
RIP Version 1 Versus RIP Version 2
A new version of RIP, called RIP version 2, expands the functionality of RIP version 1 to include:
• Variable-Length Subnet Masks (VLSMs).
• Support for next-hop addresses, which allows for optimization of routes in certain environments.
• Multicasting.
RIP version 2 packets can be multicast instead of being broadcast, reducing the load on hosts that do
not support routing protocols.
NOTE
If you are using RIP with supernetting/Classless Inter-Domain Routing (CIDR), you must use RIPv2
only. In addition, RIP route aggregation must be turned off.
Overview of OSPF
OSPF is a link-state protocol that distributes routing information between routers belonging to a single
IP domain, also known as an autonomous system (AS). In a link-state routing protocol, each router
maintains a database describing the topology of the autonomous system. Each participating router has
an identical database maintained from the perspective of that router.
From the link-state database (LSDB), each router constructs a tree of shortest paths, using itself as the
root. The shortest path tree provides the route to each destination in the autonomous system. When
several equal-cost routes to a destination exist, traffic can be distributed among them. The cost of a
route is described by a single metric.