Ericsson ECN330, User Manual

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Configuring the ECN330-switch
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• The Send Version can be specified based on these options:
• Use “RIPv1” or “RIPv2” if all routers in the local network are based
on RIPv1 or RIPv2, respectively.
• Use “RIPv1 Compatible” to propagate route information by
broadcasting to other routers on the network using the RIPv2
advertisement list, instead of multicasting as normally required by
RIPv2. (Using this mode allows RIPv1 routers to receive these
protocol messages, but still allows RIPv2 routers to receive the
additional information provided by RIPv2, including subnet mask,
next hop and authentication information.)
• Use “Do Not Send” to passively monitor route information
advertised by other routers attached to the network.
Loopback Prevention
Just as Layer 2 switches use the Spanning Tree Algorithm to prevent loops,
routers also use methods for preventing loops that would cause endless
retransmission of data traffic. When protocol packets are caught in a loop, links
will be congested, and protocol packets may be lost. However, the network will
slowly converge to the new state. RIP utilizes the following three methods that
can provide faster convergence when the network topology changes and
prevent most loops from occurring:
• Split Horizon – Never propagate routes back to an interface port from
which they have been acquired.
• Poison Reverse – Propagate routes back to an interface port from which
they have been acquired, but set the distance-vector metrics to infinity.
(This provides faster convergence.)
• Triggered Updates – Whenever a route gets changed, broadcast an
update message after waiting for a short random delay, but without
waiting for the periodic cycle.
Protocol Message Authentication
RIPv1 is not a secure protocol. Any device sending protocol messages from
UDP port 520 will be considered a router by its neighbors. Malicious or
unwanted protocol messages can be easily propagated throughout the network
if no authentication is required. RIPv2 supports authentication through a simple
password. When a router is configured to exchange authentication messages, it