Reference Guide

598 | Open Shortest Path First (OSPFv2)
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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 31-4. Enabling RFC-2328 Compliant OSPF Flooding
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 31-5. Enabling RFC-2328 Compliant OSPF Flooding
OSPF ACK Packing
The OSPF ACK Packing feature bundles multiple LS acknowledgements in a single packet, significantly
reducing the number of ACK packets transmitted when the number of LSAs increases. This feature also
enhances network utilization and reduces the number of small ACK packets sent to a neighboring router.
OSPF ACK packing is enabled by default, and non-configurable.
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 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
aid:0 chk:0xccbd aut:0 auk: keyid:0 from:Te 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
Printed only for ACK packets
No change in update packets
FTOS#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
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