Reducing The Scope Of The Lfa Calculation By Spf - Alcatel-Lucent 7450 Manual

LDP FRR Configuration
Note that because LDP can detect the loss of a neighbor/next-hop independently, it is possible that
it switches to the LFA next-hop while IGP is still using the primary next-hop. In order to avoid this
situation, it is recommended to enable IGP-LDP synchronization on the LDP interface:
config>router>interface>ldp-sync-timer seconds

Reducing the Scope of the LFA Calculation by SPF

The user can instruct IGP to not include all interfaces participating in a specific IS-IS level or
OSPF area in the SPF LFA computation. This provides a way of reducing the LFA SPF calculation
where it is not needed.
config>router>isis>level>loopfree-alternate-exclude
config>router>ospf>area>loopfree-alternate-exclude
Note that if IGP shortcut are also enabled in LFA SPF, as explained in Section 5.3.2, LSPs with
destination address in that IS-IS level or OSPF area are also not included in the LFA SPF
calculation.
The user can also exclude a specific IP interface from being included in the LFA SPF computation
by IS-IS or OSPF:
config>router>isis>interface> loopfree-alternate-exclude
config>router>ospf>area>interface> loopfree-alternate-exclude
Note that when an interface is excluded from the LFA SPF in IS-IS, it is excluded in both level 1
and level 2. When the user excludes an interface from the LFA SPF in OSPF, it is excluded in all
areas. However, the above OSPF command can only be executed under the area in which the
specified interface is primary and once enabled, the interface is excluded in that area and in all
other areas where the interface is secondary. If the user attempts to apply it to an area where the
interface is secondary, the command will fail.
Finally, the user can apply the same above commands for an OSPF instance within a VPRN
service:
config>service>vprn>ospf>area>loopfree-alternate-exclude
config>service>vprn>ospf>area>interface>loopfree-alternate-exclude
Page 554 7450 ESS MPLS Guide