From: Ricky Martin (rickycool@gmail.com)
Date: Wed Apr 27 2005 - 01:14:38 GMT-3
Hi,
Try this link http://www.cisco.com/warp/public/105/ipv6tunnel.html#configcomp
It does explain things clearly.
HTH
Ricky
On 4/27/05, ccie2be <ccie2be@nyc.rr.com> wrote:
> 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
>
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