Dell Force10 S55T S55 Configuration Guide FTOS 8.3.5.3 - Page 467
RFC-2328 Compliant OSPF Flooding,
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RFC-2328 Compliant OSPF Flooding In OSPF, flooding is the most resource-consuming task. The flooding algorithm described in RFC 2328 requires that OSPF flood LSAs on all interfaces, as governed by LSA's flooding scope. (Refer to Section 13 of the RFC.) When multiple direct links connect two routers, the RFC 2328 flooding algorithm generates significant redundant information across all links. By default, FTOS implements an enhanced flooding procedure which dynamically and intelligently detects when to optimize flooding. Wherever possible, the OSPF task attempts to reduce flooding overhead by selectively flooding on a subset of the interfaces between two routers. If RFC 2328 flooding behavior is required, enable it by using the command flood-2328 in ROUTER OSPF mode. When enabled, this command configures FTOS to flood LSAs on all interfaces. Confirm RFC 2328 flooding behavior by using the command debug ip ospf packet and look for output similar to the following: Figure 24-4. Enabling RFC-2328 Compliant OSPF Flooding 00:10:41 : OSPF(1000:00): Rcv. v:2 t:5(LSAck) l:64 Acks 2 rid:2.2.2.2 Printed only for ACK packets aid:1500 chk:0xdbee aut:0 auk: keyid:0 from:Vl 1000 LSType:Type-5 AS External id:160.1.1.0 adv:6.1.0.0 seq:0x8000000c LSType:Type-5 AS External id:160.1.2.0 adv:6.1.0.0 seq:0x8000000c 00:10:41 : OSPF(1000:00): Rcv. v:2 t:5(LSAck) l:64 Acks 2 rid:2.2.2.2 aid:1500 chk:0xdbee aut:0 auk: keyid:0 from:Vl 100 LSType:Type-5 AS External id:160.1.1.0 adv:6.1.0.0 seq:0x8000000c LSType:Type-5 AS External id:160.1.2.0 adv:6.1.0.0 seq:0x8000000c 00:10:41 : OSPF(1000:00): Rcv. v:2 t:4(LSUpd) l:100 rid:6.1.0.0 No change in update packets aid:0 chk:0xccbd aut:0 auk: keyid:0 from:Gi 10/21 Number of LSA:2 LSType:Type-5 AS External(5) Age:1 Seq:0x8000000c id:170.1.1.0 Adv:6.1.0.0 Netmask:255.255.255.0 fwd:0.0.0.0 E2, tos:0 metric:0 LSType:Type-5 AS External(5) Age:1 Seq:0x8000000c id:170.1.2.0 Adv:6.1.0.0 Netmask:255.255.255.0 fwd:0.0.0.0 E2, tos:0 metric:0 In FTOS Version, 7.5.1.0 use show ip ospf to confirm that RFC-2328 compliant OSPF flooding is enabled, as shown below. Figure 24-5. Enabling RFC-2328 Compliant OSPF Flooding Force10#show ip ospf Routing Process ospf 1 with ID 2.2.2.2 Supports only single TOS (TOS0) routes It is an Autonomous System Boundary Router It is Flooding according to RFC 2328 SPF schedule delay 5 secs, Hold time between two SPFs 10 secs Number of area in this router is 1, normal 0 stub 0 nssa 1 --More-- Open Shortest Path First (OSPFv2 and OSPFv3) | 467
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