BGP Attribute

Created: Sep 16, 2019 16:30:45Latest reply: Sep 18, 2019 02:11:05 110 3 0 0
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in BGP Route Selection Policies we have below two attributes in both have same concept as with Network command & below is IGP can any one explain that what are the difference b/w these two?


1-Prefers the manually summarized route, automatically summarized route, route imported using thenetwork command, route imported using the import-route command, and route learned from peers. These routes are in descending order of priority.


2-Prefers the route with the lowest origin type. IGP is lower than EGP, and EGP is lower than Incomplete.


because i studied origin attribute as rotue with Network command is IGP.then why these two are different attributes.?

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chenhui
Admin Created Sep 18, 2019 02:11:05 Helpful(0) Helpful(0)

Posted by LSA at 2019-09-17 18:35 these two points are two different attributes.....you said that in first is the way generating rou ...
the first rule indicates the router would prefer the routes generated from the local device, while the second rule compares the Origin value.
For example, a route with Origin value IGP is received from another router, and the same route is imported at the local router, then two routes exist.
if we follow the second rule, the routes with Origin vlaue IGP would be elected as the best one(the imported route Origin is incomplete), while the truth is not.

a

R1:
#
bgp 100
 peer 10.1.12.2 as-number 100
 peer 10.1.12.2 connect-interface GigabitEthernet0/0/0
 #
 ipv4-family unicast
  undo synchronization
  import-route direct
  peer 10.1.12.2 enable
#

R2:
#
bgp 100
 peer 10.1.12.1 as-number 100
 peer 10.1.12.1 connect-interface GigabitEthernet0/0/0
 #
 ipv4-family unicast
  undo synchronization
  network 4.4.4.4 255.255.255.255
  peer 10.1.12.1 enable
#

BGP routing table on R1:
b

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chenhui
Admin Created Sep 17, 2019 06:45:18 Helpful(0) Helpful(0)

@LSA hello, import route using the network command indicates the way itself which generates the routes(it's not an attrebute), while IGP is the BGP attribute, they are two totally different contents.

The first rule you list is the comparison of the way generating the routes, the second rule is the comparison of the origin attribute.

  • x
  • convention:

All Answers
chenhui
chenhui Admin Created Sep 17, 2019 06:45:18 Helpful(0) Helpful(0)

@LSA hello, import route using the network command indicates the way itself which generates the routes(it's not an attrebute), while IGP is the BGP attribute, they are two totally different contents.

The first rule you list is the comparison of the way generating the routes, the second rule is the comparison of the origin attribute.

  • x
  • convention:

LSA
LSA Created Sep 17, 2019 18:35:34 Helpful(0) Helpful(0)

Posted by chenhui at 2019-09-17 06:45 @LSA hello, import route using the network command indicates the way itself which generates the rout ...
these two points are two different attributes.....you said that in first is the way generating routes..but in 2nd Origin also means the way of generating routes...these two attributes are very confusing....kindly clearify ...
  • x
  • convention:

chenhui
chenhui Admin Created Sep 18, 2019 02:11:05 Helpful(0) Helpful(0)

Posted by LSA at 2019-09-17 18:35 these two points are two different attributes.....you said that in first is the way generating rou ...
the first rule indicates the router would prefer the routes generated from the local device, while the second rule compares the Origin value.
For example, a route with Origin value IGP is received from another router, and the same route is imported at the local router, then two routes exist.
if we follow the second rule, the routes with Origin vlaue IGP would be elected as the best one(the imported route Origin is incomplete), while the truth is not.

a

R1:
#
bgp 100
 peer 10.1.12.2 as-number 100
 peer 10.1.12.2 connect-interface GigabitEthernet0/0/0
 #
 ipv4-family unicast
  undo synchronization
  import-route direct
  peer 10.1.12.2 enable
#

R2:
#
bgp 100
 peer 10.1.12.1 as-number 100
 peer 10.1.12.1 connect-interface GigabitEthernet0/0/0
 #
 ipv4-family unicast
  undo synchronization
  network 4.4.4.4 255.255.255.255
  peer 10.1.12.1 enable
#

BGP routing table on R1:
b

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