3Com S7906E Configuration Manual page 1668

According to RFC 3784, the length of the IS reachability TLV (type 22) may reach the maximum of
255 octets in some cases.
For an IS-IS LSP to carry this type of TLV and to be flooded normally on all interfaces with IS-IS
enabled, the MTU of any IS-IS enabled interface, including 27 octets of LSP header and two octets
of TLV header, cannot be less than 284 octets. If an LSP must also carry the authentication
information, the minimum MTU needs to be recalculated according to the packet structure.
In a word, with the TE feature, the MTU of any interface with IS-IS enabled is recommended to be equal
to or greater than 512 octets to guarantee that IS-IS LSPs can be flooded on the network.
Follow these steps to configure IS-IS TE:
To do...
Enter system view
Enter IS-IS view
Configure the wide metric
attribute of IS-IS
Enable IS-IS TE
Configure the TLV type of the
sub-TLV carrying DS-TE
parameters
For more information about IS-IS, refer to IS-IS Configuration in the IP Routing Volume.
IS-IS TE does not support secondary IP address advertisement. With IS-IS TE enabled on an
interface configured with multiple IP addresses, IS-IS TE advertises only the primary IP address of
the interface through the sub-TLV of IS reachability TLV (type 22). You are recommended to avoid
enabling IS-IS TE on an interface configured with secondary IP addresses.
Configuring an MPLS TE explicit path
An explicit path is a set of nodes. The relationship between any two neighboring nodes on an explicit
path can be either of the following:
Strict: where the two nodes are directly connected.
Loose: where the two nodes have devices in between.
Use the command...
system-view
isis [ process-id ]
cost-style { narrow | wide |
wide-compatible |
{ compatible |
narrow-compatible }
[ relax-spf-limit ] }
traffic-eng [ level-1 | level-2 |
level-1-2 ]
te-set-subtlv lo-multiplier
value
1-19
Remarks
––
––
Required
By default, IS-IS uses narrow
metric style.
Required
Disabled by default
Optional
By default, the lo-multiplier
parameter in sub-TLV 253.