Ip Routing; Routing Information Tables - Juniper IGP - CONFIGURATION GUIDE V11.1.X Configuration Manual

ip mtu

IP Routing

The Internet is a large collection of hosts that communicate with each other and use
routers as intermediate packet switches.
Routers forward a packet through the interconnected system of networks and routers
until the packet reaches a router that is attached to the same network as the
destination host. The router delivers the packet to the specified host on its local
network.

Routing Information Tables

A router makes forwarding decisions based on the information that is contained in
its routing table. Routers announce and receive route information to and from other
routers. They build tables of routes based on the collected information about all the
best paths to all the destinations they know how to reach.
Each configured protocol has one or more local routing tables, sometimes referred
to as a routing information base (RIB). This table is a database local to the protocol
that contains all the routes known by that protocol to the prefixes in the table. For
example, OSPF might have four different routes to 10.23.40.5.32. Only one of these
routes is the best route to that prefix known to OSPF, but all four routes are in the
OSPF local routing table.
Use to force the router to ignore the DF bit if it is set in the IP packet header for
packets on an interface.
Example
host1(config-if)#ip ignore-df-bit
Use the no version to restore the default behavior, which is to consider the DF
bit before fragmentation.
See ip ignore-df-bit
Use to set the MTU size of IP packets sent on an interface.
The range is 128–10240.
Do not configure both MLPPP fragmentation (with the ppp fragmentation
command) and IP fragmentation of L2TP packets (with the ip mtu command)
on the same interface. Instead, you must choose only one of the fragmentation
configurations by setting it to the necessary value and set the other fragmentation
configuration to the maximum allowable value.
Example
host1(config-if)#ip mtu 1000
Use the no version to restore the default MTU size.
See ip mtu
Chapter 1: Configuring IP
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IP Routing