Configuring An Overload Bit For An Ipv6 Is-Is Device - Huawei Quidway NetEngine80E Configuration Manual

HUAWEI NetEngine80E/40E Router
Configuration Guide - IP Routing
l ipv6 filter-policy ipv6-prefix ipv6-prefix-name import
l ipv6 filter-policy route-policy route-policy-name import
----End

7.13.5 Configuring an Overload Bit for an IPv6 IS-IS Device

If an IS-IS device needs to be temporarily isolated, configure the IS-IS device to enter the
overload state to prevent other devices from forwarding traffic to this IS-IS device and prevent
blackhole routes.
Context
If an IS (for example, an IS to be upgraded or maintained) needs to be temporarily isolated,
configure the IS to enter the overload state so that no device will forward traffic to this IS.
IS-IS routes converge more quickly than BGP routes. To prevent blackhole routes on a network
where both IS-IS and BGP are configured, set an overload bit to instruct an IS to enter the
overload state during its start or restart. After BGP convergence is complete, cancel the overload
bit.
Issue 02 (2014-09-30)
When a filtering policy of a routing protocol is used to filter routes:
– If the action specified in an ACL rule is permit, a route that matches the rule
will be received or advertised by the system.
– If the action specified in an ACL rule is deny, a route that matches the rule will
not be received or advertised by the system.
– If a route has not matched any ACL rules, the route will not be received or
advertised by the system.
– If an ACL does not contain any rules, all routes matching the route-policy that
references the ACL will not be received or advertised by the system.
– If the ACL referenced by the route-policy does not exist, all routes matching the
route-policy will be received or advertised by the system.
– In the configuration order, the system first matches a route with a rule that has a
smaller number and then matches the route with a rule with a larger number.
Routes can be filtered using a blacklist or a whitelist:
Route filtering using a blacklist: Configure a rule with a smaller number and
specify the action deny in this rule to filter out the unwanted routes. Then,
configure another rule with a larger number in the same ACL and specify the
action permit in this rule to receive or advertise the other routes.
Route filtering using a whitelist: Configure a rule with a smaller number and
specify the action permit in this rule to permit the routes to be received or
advertised by the system. Then, configure another rule with a larger number in
the same ACL and specify the action deny in this rule to filter out unwanted
routes.
Conditions for filtering IS-IS routes are configured based on the prefix list.
Conditions for filtering IS-IS routes are configured based on the route policy.
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