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FTOS Configuration Guide for the C-Series - Force10 Networks

FTOS Configuration Guide for the C-Series - Force10 Networks

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RFC-2328 Compliant OSPF Flooding<br />

In OSPF, flooding is <strong>the</strong> most resource-consuming task. The flooding algorithm described in RFC 2328<br />

requires that OSPF flood LSAs on all interfaces, as governed by LSA's flooding scope. (Refer to Section<br />

13 of <strong>the</strong> RFC.) When multiple direct links connect two routers, <strong>the</strong> RFC 2328 flooding algorithm<br />

generates significant redundant in<strong>for</strong>mation across all links.<br />

By default, <strong>FTOS</strong> implements an enhanced flooding procedure which dynamically and intelligently detects<br />

when to optimize flooding. Wherever possible, <strong>the</strong> OSPF task attempts to reduce flooding overhead by<br />

selectively flooding on a subset of <strong>the</strong> interfaces between two routers.<br />

If RFC 2328 flooding behavior is required, enable it by using <strong>the</strong> command flood-2328 in ROUTER OSPF<br />

mode. When enabled, this command configures <strong>FTOS</strong> to flood LSAs on all interfaces.<br />

Confirm RFC 2328 flooding behavior by using <strong>the</strong> command debug ip ospf packet and look <strong>for</strong> output<br />

similar to <strong>the</strong> following:<br />

Figure 378 Enabling RFC-2328 Compliant OSPF Flooding<br />

00:10:41 : OSPF(1000:00):<br />

Rcv. v:2 t:5(LSAck) l:64 Acks 2 rid:2.2.2.2<br />

Printed only <strong>for</strong> ACK packets<br />

aid:1500 chk:0xdbee aut:0 auk: keyid:0 from:Vl 1000<br />

LSType:Type-5 AS External id:160.1.1.0 adv:6.1.0.0 seq:0x8000000c<br />

LSType:Type-5 AS External id:160.1.2.0 adv:6.1.0.0 seq:0x8000000c<br />

00:10:41 : OSPF(1000:00):<br />

Rcv. v:2 t:5(LSAck) l:64 Acks 2 rid:2.2.2.2<br />

aid:1500 chk:0xdbee aut:0 auk: keyid:0 from:Vl 100<br />

LSType:Type-5 AS External id:160.1.1.0 adv:6.1.0.0 seq:0x8000000c<br />

LSType:Type-5 AS External id:160.1.2.0 adv:6.1.0.0 seq:0x8000000c<br />

00:10:41 : OSPF(1000:00):<br />

Rcv. v:2 t:4(LSUpd) l:100 rid:6.1.0.0<br />

aid:0 chk:0xccbd aut:0 auk: keyid:0 from:Gi 10/21<br />

Number of LSA:2<br />

LSType:Type-5 AS External(5) Age:1 Seq:0x8000000c id:170.1.1.0 Adv:6.1.0.0<br />

Netmask:255.255.255.0 fwd:0.0.0.0 E2, tos:0 metric:0<br />

LSType:Type-5 AS External(5) Age:1 Seq:0x8000000c id:170.1.2.0 Adv:6.1.0.0<br />

Netmask:255.255.255.0 fwd:0.0.0.0 E2, tos:0 metric:0<br />

In <strong>FTOS</strong> Version, 7.5.1.0 use show ip ospf to confirm that RFC-2328 compliant OSPF flooding is<br />

enabled, as shown below.<br />

Figure 379 Enabling RFC-2328 Compliant OSPF Flooding<br />

<strong>Force10</strong>#show ip ospf<br />

Routing Process ospf 1 with ID 2.2.2.2<br />

Supports only single TOS (TOS0) routes<br />

It is an Autonomous System Boundary Router<br />

It is Flooding according to RFC 2328<br />

SPF schedule delay 5 secs, Hold time between two SPFs 10 secs<br />

Number of area in this router is 1, normal 0 stub 0 nssa 1<br />

--More--<br />

No change in update packets<br />

538 Open Shortest Path First

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