Can ping from PC to cisco router's ipv6 address (from LAN side) but can't ping from one pc to other's ipv6 address

[chintankothari101991]

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PCs are connected to Cisco switch and up link goes to Cisco 1841 router on router LAN side interface f0/0 ip add: 2001:xx:xx:xx:1000::64/120.  I am not able to give prefix length in Windows XP. but I can give prefix in Windows 7 machine. output of ipconfig from pc1: Ethernet Adapter Local Area Connection: Connection-specific DNS Suffix . IP Address. . . . . . . . . . . . : 192.168.1.10 Subnet Mask . . . . . . . . . . . : 255.255.255.0 IP Address. . . . . . . . . . . . : 2001:xx:xx:xx:1000::a IP Address. . . . . . . . . . . . : fe80::d465:d174:df76:f501%13 Default Gateway . . . . . . . . . : 192.168.1.100 2001:xx:xx:xx:1000::64

My problem is I can ping from PC to router's f0/0:2001:xx:xx:xx:1000::64 and from router to PC also. But I can't ping from pc1(2001:xx:xx:xx:1000::a) to pc2(2001:xx:xx:xx:1000::b) i get request timed out, whereas I can ping IPv4 address of pc2. and firewall is off on every pcs.

PC2 :ipv4 address : 192.168.1.11

         ipv6 address : 2001:xx:xx:xx:1000::b

[Seb Rupik]

Hi there,

Do you have a good reason for using a /120 mask on your user VLAN.  It is recommended that a /64 is used, see:

https://tools.ietf.org/html/rfc5375#page-30

Can you also try a ping between your two PCs using their link-local addresses (fe80::xxxx). Does that work? If that works, consider changing the f0/0 mask on the 1841 to /64 .

cheers,

Seb.

[chintankothari101991]

I tried pinging using link local address but I got request timed out only.

We thought that by using 120 prefix we can have two digits for host address like ipv4 address( 192.168.1.100 in that 100 is in hex is 64).no other reason to use /120 mask.

[Seb Rupik]

If your local-link transport is broken then global addresses will certainly fail.

If you run tcpdump/ wireshark filtering for ICMP6 do you see anything other than traffic originating from the PC you are running it from?

What is the switch (IOS version) the 1841 is connected to?

cheers,

Seb.

[chintankothari101991]

switch is sg300-28. all pcs are connected to default vlan. No other vlans are created.

does it require any exclusive configuration for ipv6 on switch. I haven't done any.

also on router i haven't given command "ipv6 unicast-routing" . i think this is not the issue , is it? because my issue is on LAN side.

Thanks,

chintan

[Seb Rupik]

Hi Chintan,

I've not had any experience of the SG300, but it is 'IPv6 ready' according to Cisco brochures.

You will need the 'ipv6 unicast-routing' command applied to you switch if you intend for your PCs to send traffic off-link via the router. The fact you do not have link-local transport is a more fundamental problem.

Have you tried running tcpdump/ wireshark on one of the PCs to look your ICMP6 traffic on the connected interface?

cheers,
Seb.

[chintankothari101991]

no i haven't tried tcpdump/wireshark !

and i'll try "ipv6 unicast-routing" on switch. if any queries i get back to you.

Thanks seb.

[chintankothari101991]

Hello seb,

Thanks seb for replies.

I have configured router's LAN side interface i.e. f0/0 with /64 subnet mask. As u said.

And now I used Linksys SR2024 which is unmanageable switch.

But I am still not getting ping from pc1 to pc2.but now I am getting ping of 

link local address of pc2 from pc1 and vice versa. 

[Seb Rupik]

Hello again,

What is the configuration of port f0/0 on the 1841 ?

On the 1841 if you run:

sh ipv6 neigh

...what is the output?

cheers,

Seb.

[chintankothari101991]

hello seb,

on interface f0/0 only given ipv4 add. and duplex auto,speed auto and ipv6 add with /64 mask.

Router#sh ipv6 neighbors
IPv6 Address                              Age Link-layer Addr State Interface
2001:E48:22:1010:1000::65                   8 8c89.a5d7.18d4  STALE Fa0/0
FE80::6E62:6DFF:FE04:215B                   3 6c62.6d04.215b  STALE Fa0/0
FE80::6E62:6DFF:FEB0:53C9                 131 6c62.6db0.53c9  STALE Fa0/0
2001:E48:22:1010:6000::12                   3 6c62.6d04.215b  STALE Fa0/0
FE80::4261:86FF:FEE4:EB95                   3 4061.86e4.eb95  STALE Fa0/0
2001:E48:22:1010:1000::B                    3 4061.86e4.eb95  STALE Fa0/0
2001:E48:22:1010:1000::F                    8 4061.86ea.d350  STALE Fa0/0
2001:E48:22:1010:1000::E                    4 6c62.6d04.2ebd  STALE Fa0/0
2001:E48:22:1010:1000::D                    4 4061.86f2.ea42  STALE Fa0/0
2001:E48:22:1010:1000::C                  131 6c62.6db0.53c9  STALE Fa0/0
2001:E48:22:1010:1000::1                    3 0080.4836.0543  STALE Fa0/0
FE80::280:48FF:FE36:543                     3 0080.4836.0543  STALE Fa0/0
FE80::F411:DD9B:4452:A2C7                  27 8c89.a5d7.18d4  STALE Fa0/0
FE80::6E62:6DFF:FE04:2EBD                   4 6c62.6d04.2ebd  STALE Fa0/0
FE80::4261:86FF:FEEA:D350                   8 4061.86ea.d350  STALE Fa0/0
FE80::4261:86FF:FEF2:EA42                   4 4061.86f2.ea42  STALE Fa0/0

in the ipv6 neighbour o/p 2001:E48:22:1010:1000::D, 2001:E48:22:1010:1000::C

address of different machines. i m not getting ping from 2001:E48:22:1010:1000::D machine to 2001:E48:22:1010:1000::C machine.

[Seb Rupik]

Are you able to post the entire config of the 1841?

Also can you set the PCs to use IPv6 auto-configuration, and see if you can ping their 2001:xx...::/64 addresses?

cheers,

Seb.

[chintankothari101991]

i can share few parts because this only part contains ipv6 . and no routing is done for ipv6 no other configuration for ipv6

ROuter#

ip cef

no ip domain lookup

no ipv6 cef

interface FastEthernet0/0

ip address 192.168.1.100 255.255.255.0

duplex auto

speed auto

ipv6 address 2001:E48:22:1010:1000::64/64

!

[vivek srivastava · Accepted solution]

Pls try with below enabled:

# ipv6 unicast-routing

# ipv6 cef

[chintankothari101991]

okay i will try this and will inform you..

thanks Vivek srivastava

[chintankothari101991]

The required command was #ipv6 unicast-routing..

thanks Vivek and Seb..