[DCN]Q&A: What Are Differences Between the Internal and External Preferences of a Router?

Created: May 21, 2019 10:32:56Latest reply: May 21, 2019 14:27:05 140 5 12 3

Routers define external preference and internal preference. Value 0 indicates direct routes and value 255 indicates routes learned from unreliable sources. A smaller value indicates a higher preference. External preferences are manually configured for routing protocols. Table 1 lists the default external preferences of routing protocols.

Table 1 Routing protocols and their default external preferences

Routing Protocol or Route Type

Default External Preference

Direct

0

OSPF

10

IS-IS

15

Static

60

RIP

100

OSPF ASE

150

OSPF NSSA

150

IBGP

255

EBGP

255

During route selection, the device first compares the external preferences of routes. When the same external preference is set for different routing protocols, the device selects the optimal route based on the internal preference. Internal preferences of routing protocols cannot be manually configured. Table 2 lists the internal preferences of routing protocols.

Table 2 Internal preferences of routing protocols

Routing Protocol or Route Type

Internal Preference

Direct

0

OSPF

10

IS-IS Level-1

15

IS-IS Level-2

18

Static

60

RIP

100

OSPF ASE

150

OSPF NSSA

150

IBGP

200

EBGP

20

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Hi_Jude     Created May 21, 2019 10:34:42 Helpful(0) Helpful(0)

very helpful
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Bruce_005     Created May 21, 2019 10:35:53 Helpful(0) Helpful(0)

Good ! Thanks!
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jack.chen     Created May 21, 2019 10:36:40 Helpful(0) Helpful(0)

very helpful
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user0017     Created May 21, 2019 10:40:12 Helpful(0) Helpful(0)

very helpful
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Thanos_Marvell     Created May 21, 2019 14:27:05 Helpful(0) Helpful(0)

It's very helpful
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