From: anthony.sequeira@thomson.com
Date: Sat Oct 28 2006 - 14:52:37 ART
Thanks so much for the analysis Pertr!
I will re-examine the exhibit and ensure it is perfectly accurate.
And thanks for your kind comments regarding the Question of the Week.
Everyone seems to really love them. . .
________________________________
From: petrsoft@gmail.com [mailto:petrsoft@gmail.com] On Behalf Of Petr
Lapukhov
Sent: Saturday, October 28, 2006 5:41 AM
To: Sequeira, Anthony (NETg)
Cc: ccielab@groupstudy.com
Subject: Re: CCIE Recertification Question of the Week - OCT2706
Anthony,
I can add a little comment here. The thing I'd like to point out is
that your exhibit looks incomplete. First, let's take a look at
the exhibit itself:
<quote>
Exhibit 1
RouterA(config)# router eigrp 100
RouterA(config-router)# network 10.0.0.0
RouterA(config-router)# network 172.16.10.0
RouterA(config-router)# exit
RouterA(config)# ip default-network 172.16.10.0
RouterA(config)# ip route 172.16.10.0 255.255.255.0 172.16.10.1
</quote>
To begin with, "ip default-network" command is CLASSFUL.
That is, when you issue "ip default-network 172.16.10.0" IOS will
generate static route like "ip route 172.16.10.0 255.255.255.0
172.16.10.1" and will not produce a default network yet.
To produce default-network you need additional statement:
"ip default-network 172.16.0.0" to be issued.
Here is a live example :)
*Before* we configure any "ip default-network command":
-------------------------------
R3#show ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS
inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route
Gateway of last resort is 110.50.13.49 to network 0.0.0.0
<snip>
144.144.0.0/24 is subnetted, 1 subnets
O E2 144.144.144.0 [110/20] via 110.50.13.50, 00:27:37,
FastEthernet0/0.5
<snip>
O*E2 0.0.0.0/0 [110/1] via 110.50.13.49, 00:27:38, FastEthernet0/0.5
-------------------
Now, we are going to make 144.144.0.0/16 a default-network. To do that,
we first issue:
R3#conf t
Enter configuration commands, one per line. End with CNTL/Z.
R3(config)#ip default-network 144.144.144.0
Some verifications:
R3(config)#do sh run | inc ip default
None found!
R3(config)#do sh run | inc ip route
ip route 144.144.0.0 255.255.0.0 144.144.144.0
A static for CLASSFUL network has been generated pointing at
original prefix. Let's see if we have new gateway of last resort:
R3(config)#do show ip route | inc Gateway of last
Gateway of last resort is 110.50.13.49 to network 0.0.0.0
Nope, it did not change!
Now, we issue yet another commad:
R3(config)#ip default-network 144.144.0.0
A CLASSFUL variant, and verify it:
R3(config)#do show run | inc ip default
ip default-network 144.144.0.0
Check the routing table:
R3(config)#do show ip route | inc Gateway of last
Gateway of last resort is 144.144.144.0 to network 144.144.0.0
R3(config)#do show ip route | inc 144.144.0.0
Gateway of last resort is 144.144.144.0 to network 144.144.0.0
* 144.144.0.0/16 is variably subnetted, 2 subnets, 2 masks
S* 144.144.0.0/16 [1/0] via 144.144.144.0
If we want to propagate the default-network to other EIGRP routers, we
may simply redistribute generated static route into EIGRP:
conf t
router eigrp 200
redistribute static
And check the neighbor's routing table (sorry for VRFs):
SW2#show ip route vrf BACKBONE
Routing Table: BACKBONE
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS
level-2
ia - IS-IS inter area, * - candidate default, U - per-user static
route
o - ODR, P - periodic downloaded static route
Gateway of last resort is 150.1.0.3 to network 144.144.0.0
D*EX 144.144.0.0/16 [170/30720] via 150.1.0.3, 00:00:10, FastEthernet0/3
13.0.0.0/24 is subnetted, 2 subnets
D 13.13.13.0 [90/156160] via 150.1.0.3, 00:41:29, FastEthernet0/3
D 13.14.13.0 [90/156160] via 150.1.0.3, 00:41:29, FastEthernet0/3
150.1.0.0/24 is subnetted, 1 subnets
C 150.1.0.0 is directly connected, FastEthernet0/3
Finally, thanks a lot for an interesting question! Default-network
is confusing topic for many of us :)
HTH
2006/10/28, anthony.sequeira@thomson.com < anthony.sequeira@thomson.com
<mailto:anthony.sequeira@thomson.com> >:
Congrats to Bajo [ bajoalex@gmail.com <mailto:bajoalex@gmail.com> ] for
winning the Cisco Press title
last
week!
We will randomly draw again this week from the responses sent to
anthony.sequeira@thomson.com . The winner will receive the CCIE Routing
and Switching Flash Cards and Exam Practice Pack from Cisco Press.
REMEMBER:
All questions will be carefully selected to have CCIE Lab relevance as
well as relevance to the written exam!
LAST WEEK'S RESPONSES:
A - 40%
B - 20%
C - 40%
D - 0%
LAST WEEK'S ANSWER:
Answer: a, b, c
Topic Domain: 4c
Issue:
How is the ip default-network used in conjunction with EIGRP?
Solution:
The network specified by the ip default-network command must be
reachable by the router that uses this command before it announces it as
a candidate default route to other EIGRP routers. The network specified
by this command must also be passed to other EIGRP routers so that those
routers can use this network as their default network and set the
gateway of last resort to this default network. The local router will
not show a gateway of last resort set - neighboring routers will show
this value as set. Multiple default networks can be configured -
neighboring routers use the EIGRP metric to determine the best default
route.
More Information:
Configuring a Gateway of Last Resort Using IP Commands
http://www.cisco.com/warp/public/105/default.html
LAST WEEK'S QUESTION:
4-5-8. Examine the configuration shown in Exhibit 1. Which statements
regarding this configuration are true? Choose all that apply.
a. For EIGRP to propagate the default route, the network specified
by the ip default-network command must be known to EIGRP
b. RouterA will not show a gateway of last resort set in the show
ip route output
c. The network specified by the ip default-network command must be
passed to other EIGRP routers
d. Multiple default networks cannot be configured
Exhibit 1
RouterA(config)# router eigrp 100
RouterA(config-router)# network 10.0.0.0
RouterA(config-router)# network 172.16.10.0
RouterA(config-router)# exit
RouterA(config)# ip default-network 172.16.10.0
RouterA(config)# ip route 172.16.10.0 255.255.255.0 172.16.10.1
THIS WEEK'S QUESTION:
2-5-2. Examine the Catalyst switch output shown in Exhibit 1. What
version of STP is in use on this switch?
a. 802.1d
b. 802.1w
c. 802.1s
d. 802.1q
Exhibit 1
ASW1#show spanning-tree vlan 1
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 32769
Address 000d.28c6.6800
Cost 19
Port 2 (FastEthernet0/2)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 000d.2903.8980
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- --------
--------------------------------
Fa0/1 Altn BLK 19 128.1 P2p
Fa0/2 Root FWD 19 128.2 P2p
Question of the Week Compliments of:
TESTiT
http://www.netmasterclass.com/site/written.php
This archive was generated by hypermail 2.1.4 : Wed Nov 01 2006 - 07:29:07 ART