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BGP redistribute-internal

Posted by MSSK , 02 December 2013 · 19,717 views

BGP redistribute-internal Elements

In this example we will examine a hidden command: bgp redistribute-internal
R1 is running OSPF with R2, iBGP with R3 (EIGRP is for loopbacks connectivity) and eBGP with R4
As known, when we redistribute BGP into a routing protocol, only eBGP routes are redistributed, let us find and see

Configuration

R1
interface Loopback0
ip address 1.1.1.1 255.255.255.255

interface FastEthernet0/0
ip address 192.168.12.1 255.255.255.0
speed 100
full-duplex

interface FastEthernet0/1
ip address 192.168.13.1 255.255.255.0
speed 100
full-duplex

interface Serial0/0
ip address 192.168.14.1 255.255.255.0
encapsulation ppp

router ospf 1
router-id 1.1.1.1
log-adjacency-changes
redistribute bgp 1 subnets
network 192.168.12.1 0.0.0.0 area 0

router eigrp 1
network 1.1.1.1 0.0.0.0
network 192.168.13.1 0.0.0.0
no auto-summary

router bgp 1
neighbor 3.3.3.3 remote-as 1
neighbor 3.3.3.3 update-source Loopback0
neighbor 192.168.14.4 remote-as 4
no auto-summary

R2

interface Loopback0
ip address 2.2.2.2 255.255.255.255

interface FastEthernet0/0
ip address 192.168.12.2 255.255.255.0
speed 100
full-duplex
router ospf 1
router-id 2.2.2.2
log-adjacency-changes
network 2.2.2.2 0.0.0.0 area 0
network 192.168.12.2 0.0.0.0 area 0

R3

interface Loopback0
ip address 3.3.3.3 255.255.255.255

interface Loopback1
ip address 13.13.13.13 255.255.255.255

interface FastEthernet0/0
ip address 192.168.13.3 255.255.255.0
speed 100
full-duplex

R3#sh run | sec router eigrp
router eigrp 1
network 3.3.3.3 0.0.0.0
network 192.168.13.3 0.0.0.0
no auto-summary

router bgp 1
network 3.3.3.3 mask 255.255.255.255
network 13.13.13.13 mask 255.255.255.255
neighbor 1.1.1.1 remote-as 1
neighbor 1.1.1.1 update-source Loopback0
no auto-summary

R4

interface Loopback0
ip address 4.4.4.4 255.255.255.255

interface Serial0/0
ip address 192.168.14.4 255.255.255.0
encapsulation ppp
clock rate 2000000

router bgp 4
network 4.4.4.4 mask 255.255.255.255
neighbor 192.168.14.1 remote-as 1
no auto-summary
Verification

Now let us check basic relations and route advertisements before we do the redistribution
R1#sh ip ospf neighbor  

Neighbor ID Pri   State    Dead Time   Address Interface
2.2.2.2    1   FULL/DR 00:00:36    192.168.12.2    FastEthernet0/0

R1#sh ip route ospf
2.0.0.0/32 is subnetted, 1 subnets
O    2.2.2.2 [110/2] via 192.168.12.2, 00:38:13, FastEthernet0/0

R1#sh ip bgp summary
BGP router identifier 1.1.1.1, local AS number 1
BGP table version is 5, main routing table version 5
3 network entries using 360 bytes of memory
3 path entries using 156 bytes of memory
3/2 BGP path/bestpath attribute entries using 372 bytes of memory
1 BGP AS-PATH entries using 24 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
Bitfield cache entries: current 2 (at peak 2) using 64 bytes of memory
BGP using 976 total bytes of memory
BGP activity 3/0 prefixes, 3/0 paths, scan interval 60 secs
Neighbor     V    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
3.3.3.3 4 1   42   41     5    0    0 00:36:19     2
192.168.14.4    4 4   41   42     5    0    0 00:37:13     1

R1#sh ip bgp
BGP table version is 5, local router ID is 1.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
  r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network   Next Hop     Metric LocPrf Weight Path
r>i3.3.3.3/32    3.3.3.3   0    100   0 i
*> 4.4.4.4/32    192.168.14.4 0 0 4 i
*>i13.13.13.13/32   3.3.3.3   0    100   0 i

R2#sh ip ospf neighbor
Neighbor ID Pri   State    Dead Time   Address Interface
1.1.1.1    1   FULL/BDR     00:00:39    192.168.12.1    FastEthernet0/0
R2#sh ip route ospf
R2#

R3#sh ip bgp summary
BGP router identifier 3.3.3.3, local AS number 1
BGP table version is 3, main routing table version 3
3 network entries using 360 bytes of memory
3 path entries using 156 bytes of memory
3/1 BGP path/bestpath attribute entries using 372 bytes of memory
1 BGP AS-PATH entries using 24 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
Bitfield cache entries: current 1 (at peak 1) using 32 bytes of memory
BGP using 944 total bytes of memory
BGP activity 3/0 prefixes, 3/0 paths, scan interval 60 secs

Neighbor     V    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
1.1.1.1 4 1   41   42     3    0    0 00:36:40     1
R3#sh ip bgp
BGP table version is 3, local router ID is 3.3.3.3
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
  r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
   Network   Next Hop     Metric LocPrf Weight Path
*> 3.3.3.3/32    0.0.0.0   0 32768 i
* i4.4.4.4/32    192.168.14.4 0    100   0 4 i
*> 13.13.13.13/32   0.0.0.0   0 32768 i
R4#sh ip bgp summary
BGP router identifier 4.4.4.4, local AS number 4
BGP table version is 4, main routing table version 4
3 network entries using 360 bytes of memory
3 path entries using 156 bytes of memory
3/2 BGP path/bestpath attribute entries using 372 bytes of memory
1 BGP AS-PATH entries using 24 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
Bitfield cache entries: current 1 (at peak 1) using 32 bytes of memory
BGP using 944 total bytes of memory
BGP activity 3/0 prefixes, 3/0 paths, scan interval 60 secs

Neighbor     V    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
192.168.14.1    4 1      42   41     4    0    0 00:37:42     2
R4#sh ip bgp
BGP table version is 4, local router ID is 4.4.4.4
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
  r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network   Next Hop     Metric LocPrf Weight Path
*> 3.3.3.3/32    192.168.14.1    0 1 i
*> 4.4.4.4/32    0.0.0.0   0 32768 i
*> 13.13.13.13/32   192.168.14.1    0 1 i

So , all is functioning normal , now let us do one way redistribution from BGP into OSPF on R1 , R2 should according to the rule we mentioned above receive only 4.4.4.4/32 (which is the prefix learned via eBGP)
R1(config)#router ospf 1
R1(config-router)#redistribute bgp 1 subnets

R2#sh ip route ospf
4.0.0.0/32 is subnetted, 1 subnets
O E2    4.4.4.4 [110/1] via 192.168.12.1, 00:00:10, FastEthernet0/0

Which is true, we cannot see the 13.13.13.13/32 prefix which is learned via iBGP, now let us add the hidden command
R1(config-router)#router bgp 1
R1(config-router)#bgp redistribute-internal
R2#sh ip route ospf
4.0.0.0/32 is subnetted, 1 subnets
O E2    4.4.4.4 [110/1] via 192.168.12.1, 00:00:51, FastEthernet0/0
13.0.0.0/32 is subnetted, 1 subnets
O E2    13.13.13.13 [110/1] via 192.168.12.1, 00:00:03, FastEthernet0/0

And yes, this command also takes the iBGP learned routes and redistributes them
And we can see the command as well in the show running configuration
R1#sh run | sec router bgp
router bgp 1
no synchronization
bgp log-neighbor-changes
bgp redistribute-internal
neighbor 3.3.3.3 remote-as 1
neighbor 3.3.3.3 update-source Loopback0
neighbor 192.168.14.4 remote-as 4
no auto-summary




thanks a lot for kind share of knowledge
You are welcome

BR,
MSSK

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