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DLSw+ Design Topologies 523
Figure 14-12
Central-Site Router Recovery
Explorer Control
The name of the game with SNA is explorer control. Explorer traffic volumes can severely
impact router CPU and network throughput. With DLSw+, routers send CANUREACH
explorer frames to each neighbor. This can result in extensive broadcast traffic trying to locate
resources. There are many different options for CCDPs to control broadcasts:
·
Filtering--The most common method for minimizing explorer traffic is to filter
unnecessary protocols and explorers. Cisco access lists in the 200 range have parameters
for addressing explorer traffic.
·
Static--Another possibility is to use static configurations. This is effective depending on
the size of the network. Static configurations eliminate broadcasts by allowing a router to
set up circuits without sending explorers. Another option if the network is large is to
statically configure only the key resources. The Cisco command icanreach is typically
used to configure static resources.
Token
Ring
IBM 3X74
IBM S/370
Cloud
Token
Ring
IBM 3X74
Router A
Router B
Router C
Central site
Router B can either be a
backup peer to Router A, or
have a concurrent session
to Router C
87200333.book Page 523 Wednesday, August 22, 2001 1:41 PM