Rfc-2328 Compliant Ospf Flooding - Dell C9000 Series Networking Configuration Manual

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, the system 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.
Enabling RFC-2328 Compliant OSPF Flooding
To enable OSPF flooding, use the following command.
When you enable this command, it configures the system to flood LSAs on all interfaces.
• Enable RFC 2328 flooding.
ROUTER OSPF mode
flood-2328
Examples of OSPF Flooding Behavior
To confirm RFC 2328 flooding behavior, use the debug ip ospf packet command.
The following example shows no change in the updated packets (shown in bold). ACKs 2 (shown in bold) is
printed only for ACK packets.
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
To confirm that you enabled RFC-2328–compliant OSPF flooding, use the show ip ospf command.
Dell#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
Open Shortest Path First (OSPFv2 and OSPFv3) 750