Summarizing Level 1 Ip Routing Information; Filtering Level 1 Ip Routing Information; Originating Default Route; Overload Bit - Extreme Networks ExtremeWare 7.2e Installation And User Manual

Interior Gateway Protocols
• Interface authentication
by inserting authentication information in the Hello PDUs and validating them on the received Hello
PDUs. You can configure authentication separately for level 1 and level 2.
• Domain or area authentication
this router. Similar to interface authentication, this is achieved by inserting the authentication
information using LSP, CSNP, and PSNP PDUs and validating them on receipt. You can configure
authentication separately for level 1 and level 2.
At each of the above levels two different authentication methods are supported: simple password as
specified in ISO/IEC 10589, and HMAC-MD5 as specified in draft-ietf-isis-hmac-00.txt.

Summarizing Level 1 IP Routing Information

Level 2 routers include in their level 2 LSPs a list of all combinations (IP address, subnet mask, and
metric) reachable in the level 1 area attached to them. This information is gathered from the level 1 LSPs
from all routers in the area. By default the combinations from all the level 1 routers are included in the
level 2 LSPs. Summarization of the level 1 combinations reduces the amount of information stored on
the level 2 router and helps in scaling to a large routing domain.
You can configure the level 1 areas with one or more combinations for announcement in their level 2
LSPs. The level 1 IP routing information is matched against the summary addresses configured on the
level 1 area. Matches are included in the level 2 LSP.
You can also configure the level 2 router to disregard the summary information. This effectively acts as
a filter, preventing reachability information from being included in the level 2 LSP.

Filtering Level 1 IP Routing Information

Level 2 routers include in their level 2 LSPs a list of all combinations (IP address, subnet mask, and
metric) reachable in the level 1 area attached to them. This information is gathered from the level 1 LSPs
from all routers in the area. By default the combinations from all the level 1 routers are included in the
level 2 LSPs. Filtering the level 1 combinations prevents the advertisement of the information to other
parts of the domain. This creates a network that is reachable only from routers within the area.
You can configure the level 1 areas in the router with an IP access profile. The level 1 IP routing
information in the level 2 LSP is matched against the access profile, and if the result is a deny, the
information is not included in the level 2 LSP.

Originating Default Route

This feature injects IP routing information for the default route in the LSP originated by the router,
thereby advertising the router as the default gateway.
Injection of the default route into the level 2 subdomain and level 1 area can be controlled individually.
You can configure the metric and metric type associated with the default route. You can also configure
the default to be automatically generated based on the presence of a default route in the kernel routing
table.

Overload Bit

This feature forces the router to set the overload bit (also known as the hippity bit) in its non-pseudo
node link-state packets. Normally the setting of the overload bit is allowed only when a router runs into
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prevents unauthorized routers from forming adjacency. This is achieved
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prevents intruders from injecting invalid routing information into
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ExtremeWare 7.2e Installation and User Guide