Dell S5148F-ON OS10 Enterprise Edition User Guide Release 10.3.2E-R1 - Page 257

Router priority

Page 257 highlights

Inter-Area-Router LSA (OSPFv3) Type 5-ASExternal LSA LSAs contain information imported into OSPF from other routing processes. Type 5 LSAs flood to all areas except stub areas. The link-state ID of the Type 5 LSA is the external network number. Type 7-NSSAExternal LSA (OSPFv2), LSA (OSPFv3) Routers in an NSSA do not receive external LSAs from ABRs but send external routing information for redistribution. They use Type 7 LSAs to tell the ABRs about these external routes, which the ABR then translates to Type 5 external LSAs and floods as normal to the rest of the OSPF network. Type 8-Link LSA (OSPFv3) Type 8 LSA carries the IPv6 address information of the local links. Type 9-Link-Local Opaque LSA (OSPFv2), IntraArea Prefix LSA (OSPFv3) Link-local opaque LSA as defined by RFC2370 for OSPFv2. Intra-Area-Prefix LSA carries the IPv6 prefixes of the router and network links for OSPFv3. Type 11-Grace LSA Link-local opaque LSA for OSPFv3 only is sent during a graceful restart by an OSPFv3 router. (OSPFv3) The LSA header is common to LSA types. Its size is 20 bytes. One of the fields of the LSA header is the link-state ID. Each router link is defined as one of four types-type 1, 2, 3, or 4. The LSA includes a link ID field that identifies the object this link connects to, by the network number and mask. Depending on the type, the link ID has different meanings. 1 Point-to-point connection to another router or neighboring router 2 Connection to a transit network IP address of the DR 3 Connection to a stub network IP network or subnet number 4 Virtual link neighboring router ID Router priority Router priority determines the designated router for the network. The default router priority is 1. When two routers are attached to a network, both attempt to become the designated router. The router with the higher router priority takes precedence. If there is a tie, the router with the higher router ID takes precedence. A router with a router priority set to zero cannot become the designated router or backup designated router. If not assigned, the system selects the router with the highest priority as the DR. The second highest priority is the BDR. Priority rates from 0 to 255, with 255 as the highest number with the highest priority. Layer 3 257

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Inter-Area-Router
LSA (OSPFv3)
Type 5—AS-
External LSA
LSAs contain information imported into OSPF from other routing processes. Type 5 LSAs
flood
to all areas except
stub areas. The link-state ID of the Type 5 LSA is the external network number.
Type 7—NSSA-
External LSA
(OSPFv2), LSA
(OSPFv3)
Routers in an NSSA do not receive external LSAs from ABRs but send external routing information for
redistribution. They use Type 7 LSAs to tell the ABRs about these external routes, which the ABR then translates
to Type 5 external LSAs and
floods
as normal to the rest of the OSPF network.
Type 8—Link LSA
(OSPFv3)
Type 8 LSA carries the IPv6 address information of the local links.
Type 9—Link-Local
Opaque LSA
(OSPFv2), Intra-
Area
Prefix
LSA
(OSPFv3)
Link-local
opaque
LSA as
defined
by RFC2370 for OSPFv2.
Intra-Area-Prefix
LSA carries the IPv6
prefixes
of the
router and network links for OSPFv3.
Type 11—Grace LSA
(OSPFv3)
Link-local
opaque
LSA for OSPFv3 only is sent during a graceful restart by an OSPFv3 router.
The LSA header is common to LSA types. Its size is 20 bytes. One of the
fields
of the LSA header is the link-state ID. Each router link is
defined
as one of four types—type 1, 2, 3, or 4. The LSA includes a link ID
field
that
identifies
the object this link connects to, by the
network number and mask. Depending on the type, the link ID has
different
meanings.
1
Point-to-point connection to another router or neighboring router
2
Connection to a transit network IP address of the DR
3
Connection to a stub network IP network or subnet number
4
Virtual link neighboring router ID
Router priority
Router priority determines the designated router for the network. The default router priority is 1. When two routers are attached to a
network, both attempt to become the designated router. The router with the higher router priority takes precedence. If there is a tie, the
router with the higher router ID takes precedence. A router with a router priority set to zero cannot become the designated router or
backup designated router.
If not assigned, the system selects the router with the highest priority as the DR. The second highest priority is the BDR. Priority rates
from 0 to 255, with 255 as the highest number with the highest priority.
Layer 3
257