What is the difference between internal preference and external preference of the routing protocols?

Created: May 21, 2019 01:36:14Latest reply: May 22, 2019 03:10:03 87 2 0 0
  Rewarded Hi-coins: 0 (problem resolved)

Will the device first compare the internal preferences ?

  • x
  • convention:

Featured Answers
DCN_Documentation
Official Created May 21, 2019 01:40:46 Helpful(0) Helpful(0)

Good day!

During route selection, the device firstly 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. 

The internal preferences of routing protocols cannot be manually configured.
  • x
  • convention:

All Answers
DCN_Documentation
DCN_Documentation Official Created May 21, 2019 01:40:46 Helpful(0) Helpful(0)

Good day!

During route selection, the device firstly 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. 

The internal preferences of routing protocols cannot be manually configured.
  • x
  • convention:

Sergio93
Sergio93 Created May 22, 2019 03:10:03 Helpful(0) Helpful(0)

Hello

Switches and routers define external and internal preferences. External preference is manually configured for each routing protocol. 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

icon-note.gif NOTE:

In Table 1, the value 0 indicates direct routes and the value 255 indicates routes learned from unreliable sources. A smaller value indicates a higher preference.

You can manually configure the external preference of all routing protocols except direct routes. The preference for each static route varies.

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

During route selection, a router first compares the external preferences of routes. When the same external preference is set for different routing protocols, the router selects the optimal route based on the internal preference. For example, assume that there are two routes to 10.1.1.0/24: a static route and an OSPF route. Both routes have the same external preference: 5. In this case, the router determines the optimal route based on the internal preference listed in Table 2. An OSPF route has an internal preference of 10, and a static route has an internal preference of 60. This indicates that the OSPF route has a higher preference than the static route, so the router selects the OSPF route as the optimal route.

icon-note.gif NOTE:
  • If multiple OSPFv2 processes learn routes to the same destination and the external and internal priorities of the routes are the same, the system selects the route with the smallest link cost; if the link costs of the routes are the same, the routes participate in load balancing. If multiple OSPFv3 processes learn routes to the same destination and the external and internal priorities of the routes are the same, the system selects the route with the smallest process ID.

  • If multiple IS-IS processes learn routes to the same destination and the external and internal priorities of the routes are the same, the system selects the route with the smallest link cost; if the link costs of the routes are the same, the routes participate in load balancing.

  • If multiple RIP or RIPng processes learn routes to the same destination and the external and internal priorities of the routes are the same, the system selects the route with the smallest link cost; if the link costs of the routes are the same, the routes participate in load balancing.

  • x
  • convention:

BEST%20ANSWER!%20If%20you%20think%20I%20earn%20it!%3Cbr%2F%3E%3Cbr%2F%3EIf%20this%20post%20was%20useful%20to%20you%2C%20please%20click%20the%20%3Cimg%20id%3D%22aimg_eYhFO%22%20onclick%3D%22zoom(this%2C%20this.src%2C%200%2C%200%2C%200)%22%20class%3D%22zoom%22%20src%3D%22https%3A%2F%2Fforum.huawei.com%2Fenterprise%2Fen%2Fstatic%2Fimage%2Fcommon%2Fsupport01.png%22%20onmouseover%3D%22img_onmouseoverfunc(this)%22%20onload%3D%22thumbImg(this)%22%20border%3D%220%22%20alt%3D%22%22%20%2F%3E%20%3Cfont%20color%3D%22DarkOrange%22%3EHelpful%3C%2Ffont%3E%20button%20and%20flag%20my%20post%20as%20a%20%26quot%3BBEST%20ANSWER%26quot%3B%20so%20others%20can%20benefit.%20Thank%20you%20%3Cimg%20id%3D%22aimg_H808i%22%20onclick%3D%22zoom(this%2C

Comment

Reply
You need to log in to reply to the post Login | Register

Notice Notice: To protect the legitimate rights and interests of you, the community, and third parties, do not release content that may bring legal risks to all parties, including but are not limited to the following:
  • Politically sensitive content
  • Content concerning pornography, gambling, and drug abuse
  • Content that may disclose or infringe upon others ' commercial secrets, intellectual properties, including trade marks, copyrights, and patents, and personal privacy
Do not share your account and password with others. All operations performed using your account will be regarded as your own actions and all consequences arising therefrom will be borne by you. For details, see " Privacy."
If the attachment button is not available, update the Adobe Flash Player to the latest version!
Login and enjoy all the member benefits

Login and enjoy all the member benefits

Login