From: ccie2be (ccie2be@nyc.rr.com)
Date: Tue Apr 26 2005 - 19:35:33 GMT-3
Simon,
Damn, you're good.
After drawing out your example, it all came together.
OK, that correction answered one of my questions and hints at the answer to
some of my other questions.
Here are some thoughts I have regarding your example. Please let me know if
I'm correct.
1. In your example, the E0 interface on both routers were assigned an
ipv6 address that shared the same major ipv6 address as the tunnel
interface. Is this required?
I think it is for this reason: Let's say host-A on R-A's side of the ipv4
network wanted to send a packet to host B on R-B's side of the ipv4 network.
I presume host A would do a DNS query for host's B address. If the ipv6
returned by DNS doesn't have the ipv4 of R-B's int S0 embedded within it,
then when R-A gets the packet from host A, it wouldn't know what to do with
it.
So, it seems to me that if 6to4 tunnels will be needed that dictates the
ipv6 addressing for each side of the ipv4 network. IOW, all ipv6 subnets on
a given side of the ipv4 network MUST begin with 2002 followed by the ipv4
embedded address, correct?
2. Your example had only 2 ipv6 domains but is there any reason there
couldn't be any number of ipv6 domains surrounding the ipv4 network?
3. Instead of using a static route which often isn't allowed in the
lab, could I just have well run an ipv6 routing protocol over the 6to4
tunnel?
4. Running a ipv6 routing protocol often requires the use of mcast
traffic. Is this supported over 6to4 tunnels?
OK, I don't have it all yet but thanks to you, I'm miles closer than I was
yesterday.
Thanks again, Tim
-----Original Message-----
From: simon hart [mailto:simon.hart@btinternet.com]
Sent: Tuesday, April 26, 2005 4:04 PM
To: simon hart; ccie2be; Group Study
Subject: RE: ipv6 6to4 tunnels
Tim,
Just reread the mail - error in the last paragraph....whoops...... should be
IPv4 address of S0 as source address and not E0. Last paragraph with
correction
Tunnel 0 will recognise that it is configured for ipv6ip 6to4 and will look
at the IPv4 address of S0 and determine the source to be 192.168.199.1 it
will now look at the destination IPv6 address 2002:ac10:1001:1::5/64, it
will strip of 2002 read the next 4 bytes and determine the destination of
the tunnel is 172.16.16.1. Hey presto we have the source and destination
address of the tunnel.
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of simon
hart
Sent: 26 April 2005 20:45
To: ccie2be; Group Study
Subject: RE: ipv6 6to4 tunnels
Hi Tim,
My understanding is that because 6to4 tunnels are by their nature automatic
then you do not explicitly define a destination address, this allows the
underlying IPv4 transport network to act as a psuedo NBMA network. Each
IPv6 network you create on the edge of the domain will have the IPv4 address
of its source tunnel embedded. I shall try and illustrate, using you're
example below
Let say RA has a S0 with an ip address of 192.168.99.1/24. Now this will be
the interface to the IPv4 domain.
Now we need to create an IPv6 Prefix for RA using this network address, the
rules state that this should be /48 address starting with 2002:: So now our
IPv6 prefix is 2002:c0a8:6301::/48 This prefix can be subnetted to create
subnets on the RA router, one for the tunnel and one for the network.
Now our IPv6 domain is on E0 of RA, so I shall assign the address
2002:c0a8:6301:1::1/64 to this interface. And to the tunnel interface I
shall assign the subnet 2002:c0a8:6301::1/64
So far so good..............
Now we have to conduct a similar exercise on RB.
RB has an S0 ipv4 address of 172.16.16.1/24. This is the interface to the
IPv4 domain.
Need to now create an IPv6 /48 prefix as above. This will result in
2002:ac10:1001::/48 From this prefix I shall create some IPv6 subnets one
for the tunnel interface and one for the E0 interface to RB's IPv6 domain.
E0 = 2002:ac10:1001:1::1/64
T0 = 2002:ac10:1001::/64
One last task to conduct on each router, I have to create a static route to
the Tunnel interfaces. On both RA and RB I shall create
ipv6 route 2002::/16 tunnel 0
This has the function that, if after performing a longest match the router
does not find a local 2002:: address it will send any packet destined to
2002:: to tunnel 0.
Now here comes the elegance of the solution!!!
A host on the subnet, lets say 2002:c0a8:6301:1::4/64 wants to send to a
host on 2002:ac10:1001:1::5/64. The IPv6 packet will be sent to the RA's E0
interface, RA will now look at its routing table and send the packet to
tunnel 0.
Tunnel 0 will recognise that it is configured for ipv6ip 6to4 and will look
at the IPv6 address of E0 and determine the source to be 192.168.199.1 it
will now look at the destination IPv6 address 2002:ac10:1001:1::5/64, it
will strip of 2002 read the next 4 bytes and determine the destination of
the tunnel is 172.16.16.1. Hey presto we have the source and destination
address of the tunnel.
Sorry for the long winded explanation, but I am not sure how to explain it
easier :(
HTH
Simon
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
ccie2be
Sent: 26 April 2005 18:51
To: Group Study
Subject: ipv6 6to4 tunnels
Hi guys,
I need some help figuring out how this works.
Let's say there are 2 ipv6 sites separated by an ipv4 domain.
ipv6 -------- r-A --- ipv4 ----- r-B ----- ipv6
I want to configure a 6to 4 tunnel between R-A and R-B.
According to the Cisco doc's, I don't need to configure a tunnel destination
on either side of the tunnel.
See this link:
http://www.cisco.com/univercd/cc/td/doc/product/software/ios123/123cgcr/ipv6
_c/sa_tunv6.htm#wp1037465
Embedded in the ipv6 address of the tunnel interface is an ipv4 address
that's local to the router on which this tunnel is configured.
That being the case, how does the one end of the tunnel find the other end?
I assume in this example, R-A and R-B don't have to share a common link,
correct?
TIA, Tim
This archive was generated by hypermail 2.1.4 : Tue May 03 2005 - 07:55:09 GMT-3