CCIE Pursuit Blog

March 17, 2009

Core Knowledge Question of the Day: 17 March 2009

Which point-to-multipoint technology utilizes an IPv4 address embedded in an IPv6 address (the IPv4 address is converted to hexadecimal and then concatenated to the prefix 2002::/16) to allow isolated IPv6 domains to be connected over an IPv4 network to remote IPv6 networks?

Highlight for answer: Automatic 6to4 Tunnels

March 12, 2009

Core Knowledge Question of the Day: 12 March 2009

Which process uses ICMP messages and solicited-node multicast addresses to determine the link-layer address of a neighbor on the same network (local link), verify the reachability of a neighbor, and track neighboring routers?

Highlight for answer: The IPv6 neighbor discovery process.

March 11, 2009

Core Knowledge Question of the Day: 11 March 2009

R1#ping FE80::2
Output Interface: Serial1/0
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to FE80::2, timeout is 2 seconds:
Packet sent with a source address of FE80::5
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/8/12 ms

Why must you specify an output interface when pinging FE80::2?

Highlight for answer: FE80::2 is an IPv6 link-local address.  IPv6 link-local address do not need to be unique on a router, but must be unique on an interface.  Because the same IPv6 link-local address can be present on multiple interfaces on a device, IOS needs to know the output interface.

December 12, 2008

Lab Tip: Review What You’ve Typed Before Blaming IOS

I was trying to apply an IPv6 address to an interface and have it use EUI-64.  For some reason I was not able to get the ‘eui-64’ option to show up.

I immediately assumed that this was a Dynamips error:

Rack1R4(config-if)#ipv add 2001:CC1E:x:404::/64 ?
X:X:X:X::X/<0-128>  IPv6 prefix

Rack1R4(config-if)#ipv add 2001:CC1E:x:404:: ?
X:X:X:X::X/<0-128>  IPv6 prefix

Rack1R4(config-if)#ipv add 2001:CC1E:x:404::/64 ?
X:X:X:X::X/<0-128>  IPv6 prefix

Rack1R4(config-if)#ipv add 2001:CC1E:x:404::/64
% Incomplete command.

DOH!!!!  That ‘x’ was supposed to be a ‘1’ (x is a variable that you’re supposed to fill in with your rack number).  I was a bit too literal in my task interpretation.  🙂  This was a PEBKAC error and not a Dynamips issue.

But ‘x’ is not a hexadecimal character (0 – 9 and A – F) so why didn’t IOS throw an error?

Rack1R4(config-if)#ipv6 address ?
WORD                General prefix name
X:X:X:X::X          IPv6 link-local address
X:X:X:X::X/<0-128>  IPv6 prefix
autoconfig          Obtain address using autoconfiguration

Ah. IOS thought that I had configured the “general prefix name” and was expecting the address to follow.

I typed the address correctly and all was well:

Rack1R4(config-if)#ipv6 address 2001:CC1E:1:404::/64 eui-6

August 17, 2008

Lab Tip: IPv6 EUI-64 Unexpected (For Me) Behavior

I ran across an unexpected behavior with IPv6 EUI-64 addressing today.  I had configured an interface with EUI-64 addressing.  Knowing that I would need to run OSPFv3 over this Frame Relay interface, I followed my normal procedure of creating a simplified link-local address.  To my surprise, this link-local address changed my EUI-64 address:

interface Serial0/0
 ipv6 address 2001:CC1E:1:1515::/64 eui-64
 ipv6 address FE80::1 link-local

r1(config-if)#do sh ipv int br | sec l0/0
Serial0/0                  [up/up]

For some reason the EUI-64 part of the IPv6 address was replaced with the host address of the link-local address.

Let’s recreate the scenario by stripping off the IPv6 addressing:

r1(config-if)#int s0/0
r1(config-if)#no ipv6 address 2001:CC1E:1:1515::/64 eui-64
r1(config-if)#no ipv6 address FE80::1 link-local

r1(config-if)#do sh run int s0/0 | i l0/0|ipv
interface Serial0/0

r1(config-if)#do sh ipv int br | sec l0/0
Serial0/0                  [up/up]

Now configure the EUI-64 address:

r1(config-if)#int s0/0
r1(config-if)#ipv6 address 2001:CC1E:1:1515::/64 eui-64

r1(config-if)#do sh ipv int br | sec l0/0
Serial0/0                  [up/up]

Now create add a link-local address:

r1(config-if)#int s0/0
r1(config-if)#ipv add FE80::1 link-local

r1(config-if)#do sh ipv int br | sec l0/0
Serial0/0                  [up/up]

It’s good to know about this behavior in case you get a task that asks you to use an EUI-64 address.  Depending on the grading method, you could lose points for this.

June 6, 2008

IPv6 Ping Test Characters

Filed under: Cisco,Cisco Certification,IOS,IPv6 — cciepursuit @ 12:45 pm
Tags: , ,

I recently posted about a strange ping return character:

r5(config-if)#do p 2001:173:1:57::7

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:173:1:57::7, timeout is 2 seconds:
Success rate is 0 percent (0/5)

Props to Geoff for pointing out that this is an IPv6 PING Character:

ping ipv6

Table 41 ping Test Characters (IPv6) 


Each exclamation point indicates receipt of a reply.


Each period indicates that the network server timed out while waiting for a reply.


Unknown error.


Unreachable for unknown reason.


Administratively unreachable. Usually, this output indicates that an access list is blocking traffic.


Packet too big.


Host unreachable.


Network unreachable (beyond scope).


Port unreachable.


Parameter problem.


Time exceeded.


No route to host.

April 29, 2008

Internetwork Expert Volume II: Lab 5 – Section 6

IPv6 – 12 Points

6.1 IPv6 Addressing

Very basic IPv6 addressing task.

6.2 IPv6 over Frame Relay

Easy IPv6 over Frame Relay task. 

The IE solution configured a link-local address on r1 and r3.  I did not.  This is a point-to-point connection so I saw no need for a link-local address.

Task 6.2

I did configure the link-local addresses on r2, r3, and r4 (along with frame maps) but it looks like those addresses and maps were not needed (actually, they used them later in the BGP IPv6 sections).

6.3 IPv6 BGP Advertisements

6.4 IPv6 BGP Summarization

6.5 IPV6 BGP

Since IPv6 BGP is not on the exam I simply read the solution guide for task 6.3 – 5 and configured my routers to match.

April 17, 2008

OSPFv3 Router-ID Uses IPv4 Address

Filed under: Cisco,Cisco Certification,IOS,IPv6,OSPF — cciepursuit @ 8:37 am
Tags: , , , , ,

Ivan Pepelnjak over at Cisco IOS Hint and Tricks (an absolute must-read site) has a nice post about the use of IPv4 addresses as the router ID in OSPFv3.  I touched on this in this Question of the Day.

This part of the post made me laugh out loud:

One of the obscure facts of IPv6 OSPF (OSPFv3) is that it uses a 32-bit router ID like OSPFv2. It’s a reasonable choice, I haven’t seen an OSPF network with more than a billion routers yet.

I love the “yet” qualifier.  🙂

—Read The Rest Here—

April 8, 2008

Question Of The Day: 08 April, 2008

Topic: IPv6

Router r1 is running OSPFv3:

r1#show ip interface brief | e ass
Interface                  IP-Address      OK? Method Status                Protocol
Serial1/0.12            YES NVRAM  up                    up     
Serial1/0.13            YES NVRAM  up                    up     
Loopback0                 YES NVRAM  up                    up     
Loopback1             YES NVRAM  up                    up     
Loopback2             YES NVRAM  up                    up     
Loopback3             YES NVRAM  up                    up   

r1#show ip interface brief
Serial1/0                  [up/up]
Serial1/0.12               [up/up]
Serial1/0.13               [up/up]
Loopback0                  [up/up]
Loopback1                  [up/up]
Loopback2                  [up/up]
Loopback3                  [up/up]

r1#show ip protocols summary
Index Process Name
0     connected
1     static

r1#show ipv6 protocols summary
Index Process Name
0      connected
1      static
2      ospf 100

r1#show ipv6 ospf interface
Serial1/0.12 is up, line protocol is up
  Link Local Address FE80::CE00:20FF:FE78:0, Interface ID 15
  Area 0, Process ID 100, Instance ID 0, Router ID ????
  Network Type POINT_TO_POINT, Cost: 64
  Transmit Delay is 1 sec, State POINT_TO_POINT,
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
    Hello due in 00:00:00
  Index 1/1/1, flood queue length 0
  Next 0x0(0)/0x0(0)/0x0(0)
  Last flood scan length is 0, maximum is 0
  Last flood scan time is 0 msec, maximum is 0 msec
  Neighbor Count is 0, Adjacent neighbor count is 0
  Suppress hello for 0 neighbor(s)

r1#show run | sec ipv6 ospf|router-id
 ipv6 ospf 100 area 0

What is the OSPFv3 router-id of r1?

Click Here For Answers

Yesterday’s Question

Question Of The Day: 07 April, 2008 

Topic: IP Prefix Lists

Write an IP prefix list called “NO_DEFAULT” that allows all routes except the default route.

 ip prefix-list NO_DEFAULT sequence 10 deny
 ip prefix-list NO_DEFAULT sequence 20 permit le 32

IP prefix lists are something that you’ll need to know well for the CCIE lab.  This example uses two of the most important prefix-lists to know: the ‘all prefixes list’ and the ‘default route prefix list’.

ip prefix-list

April 5, 2008

Internetwork Expert Volume II: Lab 6 – Section 6

IPv6 – 7 Points

6.1 IPv6 Addressing

Easy task, but I’m not sure why the IE solution uses eui-64 addressing for fa0/0 on r3?

Task 6.1 – IPv6

6.2 RIPng

Configure RIPng on all interfaces running IPv6.  Have r3 originate a default route to r2.  r2 should not see any of the specific subnets learned from BB2, but don’t use a prefix-list to accomplish this.

NOTE: Don’t forget to disable split-horizon on r1 (FR hub).

I’d love to give you a link to the DOCCD for some of these commands, but Cisco has completely fucked up the IPv6 documentation.

r3(config-if)#int s0/3:0
r3(config-if)#ipv rip RIPng en
r3(config-if)#ipv rip RIPng ?
  default-information  Configure handling of default route

r3(config-if)#ipv rip RIPng default-information ?
  only       Advertise only the default route
  originate  Originate the default route

r3(config-if)#ipv rip RIPng default-information only

r2#sh ipv route rip
IPv6 Routing Table – 8 entries
Codes: C – Connected, L – Local, S – Static, R – RIP, B – BGP
       U – Per-user Static route, M – MIPv6
       I1 – ISIS L1, I2 – ISIS L2, IA – ISIS interarea, IS – ISIS summary
       O – OSPF intra, OI – OSPF inter, OE1 – OSPF ext 1, OE2 – OSPF ext 2
       ON1 – OSPF NSSA ext 1, ON2 – OSPF NSSA ext 2
       D – EIGRP, EX – EIGRP external
R   ::/0 [120/2]
     via FE80::211:93FF:FEB0:9DA0, Serial0/1/0

R   2001:192:10:1::/64 [120/2]
     via FE80::211:93FF:FEB0:9DA0, Serial0/1/0
R   2001:CC1E:1:5::/64 [120/3]
     via FE80::1, Serial0/0/0

6.3 RIPng Summarization

Configrue r3 to advertise a single /48 summary of all of the IPv6 addresses.

r3(config)#int fa0/0
r3(config-if)#ipv6 rip RIPng summary-address 2001:CC1E:1::/48

r3#debug ipv6 rip fa0/0
RIP Routing Protocol debugging is on for interface FastEthernet0/0
*Mar  1 22:31:38: RIPng: Sending multicast update on FastEthernet0/0 for RIPng
*Mar  1 22:31:38:        src=FE80::211:93FF:FEB0:9DA0
*Mar  1 22:31:38:        dst=FF02::9 (FastEthernet0/0)
*Mar  1 22:31:38:        sport=521, dport=521, length=52
*Mar  1 22:31:38:        command=2, version=1, mbz=0, #rte=2
*Mar  1 22:31:38:        tag=0, metric=1, prefix=2001:192:10:1::/64
*Mar  1 22:31:38:       tag=0, metric=1, prefix=2001:CC1E:1::/48 


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