HP 5500 EI series Configuration Manual page 153

Enabling LSP fragment extension
Perform this task to enable IS-IS fragment extension for an IS-IS process. The MTUs of all interfaces
running the IS-IS process must not be less than 512. Otherwise, LSP fragment extension does not take
effect.
To enable LSP fragment extension:
Step
1. Enter system view.
2. Enter IS-IS view.
3. Enable LSP fragment
extension.
4. Configure a virtual system
ID.
Limiting LSP flooding
In NBMA networks such as ATM and FR, many P2P links exist. As shown in
and D run IS-IS. When Router A generates an LSP, it floods the LSP out of Ethernet 1/1, Ethernet 1/2 and
Ethernet 1/3. After Router D receives the LSP from Ethernet 1/3, it floods it out of Ethernet 1/1 and
Ethernet 1/2 to Router B and Router C. However, Router B and Router C have already received the LSP
from Router A. Repeated LSP flooding consumes extra bandwidth.
Figure 38 Network diagram of a fully meshed network
Router A
Eth1/1
Eth1/2
Eth1/3
Eth1/1
Eth1/2
Eth1/3
Router B
To avoid this problem, you can add interfaces to a mesh group or block some interfaces.
• An interface in a mesh group floods a received LSP only to interfaces not in the mesh group.
A blocked interface sends LSPs only after receiving LSP requests.
•
Before you configure this task, you must consider redundancy for interfaces in case LSP packets cannot
be flooded because of link failures.
To add an interface to a mesh group or block an interface:
Command
system-view
isis [ process-id ] [ vpn-instance
vpn-instance-name ]
lsp-fragments-extend [ level-1 |
level-1-2 | level-2 ]
virtual-system virtual-system-id
Router D
Eth1/3
Eth1/2
Eth1/1
Eth1/1
Eth1/2
Eth1/3
Router C
142
Remarks
N/A
N/A
By default, this feature is disabled.
By default, no virtual system ID is
configured.
Configure at least one virtual system to
generate extended LSP fragments.
Figure 38, Routers A, B, C