Cisco CCNA / CCNP Certification: OSPF E2 vs. E1 Routes

Cisco CCNA / CCNP Certification: OSPF E2 vs

Cisco CCNA / CCNP Certification: OSPF E2 vs. E1 Routes

OSPF is a serious subject on both the CCNA and CCNP exams, and it is also the subject that requires probably the most consideration to detail. The place dynamic routing protocols reminiscent of RIP and IGRP have only one router kind, a have a look at a Cisco routing desk shows several totally different OSPF route types.

R1show ip route

Codes: C - linked, S - static, I - IGRP, R - RIP, M - cellular, B - BGP

D - EIGRP, EX - EIGRP exterior, O - OSPF, IA - OSPF inter area

N1 - OSPF NSSA exterior kind 1, N2 - OSPF NSSA external sort 2

E1 - OSPF external sort 1, E2 - OSPF exterior kind 2, E - EGP

In this tutorial, we'll check out the distinction between of those route varieties, E1 and E2.

Route redistribution is the process of taking routes realized via one routing protocol and injecting those routes into another routing domain. (Static and connected routes will also be redistributed.) When a router working OSPF takes routes realized by one other routing protocol and makes them accessible to the opposite OSPF-enabled routers it's communicating with, that router becomes an Autonomous System Border Router (ASBR).

Let's work with an example the place R1 is working each OSPF and RIP. R4 is in the same OSPF domain as R1, and we want R4 to study the routes that R1 is learning via RIP. This means we have now to carry out route redistribution on the ASBR. The routes that are being redistributed from RIP into OSPF will seem as E2 routes on R4:

R4show ip route ospf

O E2 5.1.1.1 [110/20] through 172.34.34.3, 00:33:21, Ethernet0

6.0.0.zero/32 is subnetted, 1 subnets

O E2 6.1.1.1 [110/20] by way of 172.34.34.3, 00:33:21, Ethernet0

172.12.0.zero/16 is variably subnetted, 2 subnets, 2 masks

O E2 172.12.21.zero/30 [110/20] through 172.34.34.3, 00:33:32,

Ethernet0

O E2 7.1.1.1 [110/20] through 172.34.34.3, 00:33:21, Ethernet0

15.0.0.0/24 is subnetted, 1 subnets

O E2 15.1.1.0 [110/20] by way of 172.34.34.three, 00:33:32, Ethernet0

E2 is the default route type for routes realized by way of redistribution. The key with E2 routes is that the price of these routes reflects only the price of the path from the ASBR to the ultimate destination; the cost of the trail from R4 to R1 is just not reflected on this cost. (Do not forget that OSPF's metric for a path is known as "price".)

In this example, we would like the cost of the routes to mirror the entire path, not just the path between the ASBR and the vacation spot network. To do so, the routes must be redistributed into OSPF as E1 routes on the ASBR, as shown here.

R1conf t

Enter configuration commands, one per line. Finish with CNTL/Z.

R1(config)router ospf 1

R1(config-router)redistribute rip subnets metric-sort 1

Now on R4, the routes seem as E1 routes and have a larger metric, for the reason that whole path value is now reflected within the routing table.

O E1 5.1.1.1 [110/94] via 172.34.34.3, 00:33:21, Ethernet0

6.0.0.zero/32 is subnetted, 1 subnets

O E1 6.1.1.1 [110/100] by way of 172.34.34.3, 00:33:21, Ethernet0

172.12.0.zero/16 is variably subnetted, 2 subnets, 2 masks

O E1 172.12.21.0/30 [110/94] by way of 172.34.34.three, 00:33:32, Ethernet0

O E1 7.1.1.1 [110/94] through 172.34.34.three, 00:33:21, Ethernet0

15.0.0.zero/24 is subnetted, 1 subnets

O E1 15.1.1.0 [110/94] through 172.34.34.3, 00:33:32, Ethernet0

Realizing the difference between E1 and E2 routes is significant for CCNP exam success, in addition to absolutely understanding a manufacturing router's routing table. Good luck in your research!

CCNA and CCNP candidates are effectively-versed in Spanning-Tree Protocol, and one of many nice things about STP is that it works nicely with little or no extra configuration. There may be one scenario where STP works towards us only a bit whereas it prevents switching loops, and that's the scenario where switches have multiple bodily connections.

You'd assume that when you've got two separate physical connections between switches, twice as a lot information might be sent from one swap to the opposite than if there was just one connection. STP does not enable this by default, nevertheless in an effort to prevent switching loops from forming, one of the paths will probably be blocked.

SW1 and SW2 are related through two separate physical connections, on ports fast0/eleven and quick zero/12. As we will see here on SW1, only port zero/11 is actually forwarding traffic. STP has put the opposite port into blocking mode (BLK).

SW1show spanning vlan 10

(some output removed for readability)

Interface Role Sts Value Prio.Nbr Kind

Fa0/eleven Root FWD 19 128.eleven P2p

Fa0/12 Altn BLK 19 128.12 P2p

While STP helps us by stopping switching loops, STP is also hurting us by stopping us from using a perfectly valid path between SW1 and SW2. We might actually double the bandwidth obtainable between the 2 switches if we might use that path that's presently being blocked.

The key to using the at the moment blocked path is configuring an Etherchannel. An Etherchannel is just a logical bundling of two - eight physical connections between two Cisco switches.

Configuring an Etherchannel is actually quite simple. Use the command "channel-group 1 mode on" on every port you need to be placed into the Etherchannel. Of course, this must be carried out on each switches should you configure an Etherchannel on one swap and don't achieve this on the right ports on the other swap, the line protocol will go down and keep there.

The great thing about an Etherchannel is that STP sees the Etherchannel as one connection. If any of the bodily connections inside the Etherchannel go down, STP doesn't see this, and STP won't recalculate. While visitors stream between the two switches will obviously be slowed, the delay in transmission caused by an STP recalculation is avoided. An Etherchannel additionally allows us to make use of multiple physical connections at one time.

Here's easy methods to put these ports into an Etherchannel:

SW1conf t

Enter configuration commands, one per line. End with CNTL/Z.

SW1(config)interface quick 0/11

SW1(config-if)channel-group 1 mode on

Creating a port-channel interface Port-channel 1

SW1(config-if)interface quick zero/12

SW1(config-if)channel-group 1 mode on

SW2conf t

Enter configuration commands, one per line. End with CNTL/Z.

SW2(config)int quick 0/eleven

SW2(config-if)channel-group 1 mode on

SW2(config-if)int fast 0/12

SW2(config-if)channel-group 1 mode on

The command "present interface trunk" and "present spanning-tree vlan 10" will likely be used to verify the Etherchannel configuration.

SW2show interface trunk (some output removed for clarity)

Port Mode Encapsulation Standing Native vlan

Po1 desirable 802.1q trunking 1

SW2show spanning vlan 10 (some output removed for readability

POST COMMENT

Cisco CCNA Certification: The Importance Of The OSI Mannequin Cisco CCNA Certification: The Worth Of The CCNA And CCNP Cisco CCNA Certification: Defining And Creating Collision Domains Cisco CCNA Certification Tutorial: Segmenting Your Community National Hockey League Teams up with Cisco Flip Cisco Certification Brain Dumps Additional Features of Cisco E4200 that Not Exist in Previous Linksys Version! Cisco 642-974 Test Microsoft, Hewlett-Packard to Cisco inventory from the top ten competitors (2) What Are the Benefits of Being Cisco Certified? Microsoft, Hewlett-Packard to Cisco inventory from the top ten competitors (3) Cisco CCNA Voice Certification Cisco WRT54GL