Konfigurasi iBGP dan eBGP

Note : C1 adalah cloud yang merupakan simulasi 2 buah PC yang berbeda. PC1 merupakan user di network R1, ip:172.16.1.2/24. Sedangkan PC2 merupakan user di network R3, ip:10.3.3.2/24. Untuk simulasi PC ini saya menggunakan software vpcs yang bisa terintegrasi dengan GNS3.

Berdasarkan topologi diatas, ada dua konfigurasi iBGP yang bisa diterapkan. Yang pertama peering ke interface point-to-point, yang kedua peering ke loopback. Disini akan dibahas satu persatu, dan bisa dilihat perbedaan konfigurasinya.

EIGRP Route Filtering : Route-Map

Route-map is a rule on Router for modification routing information. Its can use for determine path, filtering, etc. At this post I will make a sample route-map for filtering on eigrp routing protocol. Refer to Figure 1 below, i just use two router, in fact on HO Environment will be a few router and switch. See HO configuration, I assume others network devices with a loopback address, you can see in description loopback interface.

EIGRP Route Filtering : Prefix-List

For Filtering route information on EIGRP we can use Distribute-List. And for grab ip address that will be filtered, can use : access-list, prefix-list, and route-map. At this time I will use Prefix-List, for configuration please follow step below :

1. Makes topology and create ip addresses like this figure
2. Create eigrp routing AS 10 and advertise all self-interface network on each router
3. Make sure all routers form a neighborship (show ip eigrp neighbors) and exchange routing information (show ip route eigrp)
4.  Issue this configuration on R1 :

R1(config)#router eigrp 10
R1(config-router)#distribute-list prefix semeru out Serial0
R1(config-router)#exit
R1(config)#ip prefix-list semeru seq 5 deny 192.168.1.0/24 ge 32
R1(config)#ip prefix-list semeru seq 10 permit 0.0.0.0/0 le 32
R1(config)#

5.  Issue this configuration on R3 :

R3(config)#router eigrp 10
R3(config-router)#distribute-list prefix lawu out Serial1
R3(config-router)#exit
R3(config)#ip prefix-list lawu seq 5 deny 192.168.3.0/24 ge 32
R3(config)#ip prefix-list lawu seq 10 permit 0.0.0.0/0 le 32
R3(config)#

Note : IOS requires that the configured prefix-length, ge-value, and le-value meet the following requirements : prefix-length <= ge-value <= le-value. Otherwise, IOS rejects the ip prefix-list command.
192.168.1.0/24 ge 32 matches route 192.168.1.1/32 – 192.168.1.254/32 but not 192.168.1.0/24 subnet.

Now you can issue this command below for verified :

R2#show ip route eigrp
172.16.0.0/31 is subnetted, 3 subnets
D       172.16.2.0 [90/2681856] via 172.16.1.0, 00:09:47, Serial0
[90/2681856] via 172.16.3.1, 00:09:47, Serial1
192.168.1.0/32 is subnetted, 3 subnets
D       192.168.1.1 [90/2809856] via 172.16.3.1, 00:09:47, Serial1
D       192.168.1.3 [90/2809856] via 172.16.3.1, 00:09:47, Serial1
D       192.168.1.2 [90/2809856] via 172.16.3.1, 00:09:47, Serial1
192.168.3.0/32 is subnetted, 3 subnets
D       192.168.3.3 [90/2809856] via 172.16.1.0, 00:11:56, Serial0
D       192.168.3.2 [90/2809856] via 172.16.1.0, 00:11:56, Serial0
D       192.168.3.1 [90/2809856] via 172.16.1.0, 00:11:56, Serial0
R2#

By output above, we can see subnet on R1 out via R3, and subnet on R3 out via R1. If eigrp dont filter route information, each subnet on router will out via each router self.
It just a simple sample, in fact route filtering will be very useful, so You must expand the configuration according the requirements.

Sedikit catatan : WAN Optimization

WAN OPTIMIZATION adalah metode untuk mengoptimalkan kinerja Jaringan WAN. Metode yang digunakan bisa berupa compression, caching, trafic shaping, dll. Saat ini sudah banyak appliances WAN Optimization atau biasa juga disebut WAN Accelerator seperti ; Riverbed, Blue Coat, Cisco WAAS, Juniper Networks WAN Accelereation.
Konsep compression di WAN Accelerator mirip dengan software compression pada umumnya (rar, zip, dll). Data yang di compress adalah Header dari data tersebut tanpa mengganggu Payload nya, jadi kualitas file tidak terganggu. Dalam penggunaan WAN Accelerator harus benar-benar memperhatikan data apa saja yang dilewatinya, jangan sampai ada yang tidak support dengan WAN Acceleratornya. Jika hal itu terjadi, data hasil compress malah akan menjadi lebih besar berkali-kali lipat (sudah ada kasus seperti ini).

WAN Accelerator biasa dipasang dibelakang router yang kearah LAN. Ada dua mode yang bisa digunakan ; sebagai router dan bridge.

OSPF over Multipoint Frame Relay

Configuring Multipoint OSPF using Network type Point-to-Multipoint

R1#sh run
!
Output Omitted
!
interface FastEthernet0
 no ip address
 shutdown
 speed auto
!
interface Serial0
 no ip address
 encapsulation frame-relay
!
interface Serial0.1 multipoint
 ip address 10.2.123.1 255.255.255.248
 ip ospf network point-to-multipoint
 frame-relay interface-dlci 102
 frame-relay interface-dlci 103
!
end

R1#sh ip ospf neighbo

Neighbor ID     Pri   State           Dead Time   Address         Interface
3.3.3.3           0   FULL/  -        00:01:50    10.2.123.3      Serial0.1
2.2.2.2           0   FULL/  -        00:01:51    10.2.123.2      Serial0.1
R1#sh ip ospf interface s0.1
Serial0.1 is up, line protocol is up
  Internet Address 10.2.123.1/29, Area 0
  Process ID 1, Router ID 1.1.1.1, Network Type POINT_TO_MULTIPOINT, Cost: 64
  Transmit Delay is 1 sec, State POINT_TO_MULTIPOINT,
  Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5
    oob-resync timeout 120
    Hello due in 00:00:13
  Index 1/1, flood queue length 0
  Next 0x0(0)/0x0(0)
  Last flood scan length is 1, maximum is 1
  Last flood scan time is 4 msec, maximum is 4 msec
  Neighbor Count is 2, Adjacent neighbor count is 2
    Adjacent with neighbor 3.3.3.3
    Adjacent with neighbor 2.2.2.2
  Suppress hello for 0 neighbor(s)
R1#

R2#sh run
!
Output Omitted
!
interface FastEthernet0
 no ip address
 shutdown
 speed auto
!
interface Serial0
 no ip address
 encapsulation frame-relay
!
interface Serial0.1 multipoint
 ip address 10.2.123.2 255.255.255.248
 ip ospf network point-to-multipoint
 frame-relay map ip 10.2.123.3 101 broadcast
 frame-relay interface-dlci 101
!
router ospf 1
 router-id 2.2.2.2
 log-adjacency-changes
 network 10.0.0.0 0.255.255.255 area 0
!
end

R2#sh ip ospf neig

Neighbor ID     Pri   State           Dead Time   Address         Interface
1.1.1.1           0   FULL/  -        00:01:54    10.2.123.1      Serial0.1
R2#sh ip ospf interface s0.1
Serial0.1 is up, line protocol is up
  Internet Address 10.2.123.2/29, Area 0
  Process ID 1, Router ID 2.2.2.2, Network Type POINT_TO_MULTIPOINT, Cost: 64
  Transmit Delay is 1 sec, State POINT_TO_MULTIPOINT,
  Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5
    oob-resync timeout 120
    Hello due in 00:00:17
  Index 1/1, flood queue length 0
  Next 0x0(0)/0x0(0)
  Last flood scan length is 1, maximum is 1
  Last flood scan time is 4 msec, maximum is 4 msec
  Neighbor Count is 1, Adjacent neighbor count is 1
    Adjacent with neighbor 1.1.1.1
  Suppress hello for 0 neighbor(s)
R2#

R3#sh run
Building configuration...

Current configuration : 933 bytes
!
Output Omitted
!
interface Serial0
 no ip address
 encapsulation frame-relay
!
interface Serial0.1 multipoint
 ip address 10.2.123.3 255.255.255.248
 ip ospf network point-to-multipoint
 frame-relay map ip 10.2.123.2 101 broadcast
 frame-relay interface-dlci 101
!
router ospf 1
 router-id 3.3.3.3
 log-adjacency-changes
 network 10.0.0.0 0.255.255.255 area 0
!
end

R3#sh ip ospf neighbor

Neighbor ID     Pri   State           Dead Time   Address         Interface
1.1.1.1           0   FULL/  -        00:01:43    10.2.123.1      Serial0.1
R3#sh ip ospf interface s0.1
Serial0.1 is up, line protocol is up
  Internet Address 10.2.123.3/29, Area 0
  Process ID 1, Router ID 3.3.3.3, Network Type POINT_TO_MULTIPOINT, Cost: 64
  Transmit Delay is 1 sec, State POINT_TO_MULTIPOINT,
  Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5
    oob-resync timeout 120
    Hello due in 00:00:07
  Index 1/1, flood queue length 0
  Next 0x0(0)/0x0(0)
  Last flood scan length is 1, maximum is 1
  Last flood scan time is 0 msec, maximum is 0 msec
  Neighbor Count is 1, Adjacent neighbor count is 1
    Adjacent with neighbor 1.1.1.1
  Suppress hello for 0 neighbor(s)
R3#

OSPF Virtual Link

An OSPF Virtual Link allow two backbone area connected trough each ABR. The two ABRs form a neighbor relationship through the same nonbackbone area with that virtual link, even when separated by many other routers and subnets.
Example, two Company want to connect they nonbackbone area respectively. It makes there are two backbone area exist, and OSPF requires that backbone area be contiguous. To solve this problem, we will configures a virtual link between ABRs C1 and C2. The virtual link exists inside area 0, making area 0 contiguous.

The two ABRs will send their LSDB to each others as a unicast packet over virtual link, —the other router in nonbackbone area just forward this packet— so that all routers in both parts of area 0 learn the routes from the other area 0.  In this concept, LSA mark the Do Not Age (DNA), meaning that all routers on the other side of the virtual link will not expects the LSAs to be reflooded over the virtual link on the usual 30 minutes refresh interval, it helps reduce overhead over the virtual link.