From: Scott M Vermillion (scott_ccie_list@it-ag.com)
Date: Sun Mar 08 2009 - 20:26:40 ARST
GRE overhead is eight bytes when a tunnel key is involved; it is
otherwise only four bytes. For example, IIRC, a tunnel key would be
present in certain DMVPN applications.
On Mar 8, 2009, at 12:22 , Daniel Kutchin wrote:
> Was wondering how to demonstrate the diff in packet sizes using ping.
>
>
>
> Pinging an IPv6/GRE/IP tunnel used packet lengths of 124:
>
>
> *Mar 1 01:40:41.202: IP: s=10.10.10.10 (Tunnel12), d=10.20.20.20
> (Ethernet0/0.12), len 124, sending, proto=47 <-- GRE
> ^^^^^^^
>
>
>
> Whereas an IPv6/IP tunnel used ping packet sizes of 120:
>
>
> *Mar 1 02:56:28.296: IP: s=10.10.10.10 (Tunnel12), d=10.20.20.20
> (Ethernet0/0.12), len 120, sending, proto=41 <-- IPv6IP
> ^^^^^^^
>
>
> I obtained a packet size difference of 4 not 8 ...hmm.. any hint?
>
>
>
> Here is the setup:
>
> R1:
> interface Loopback0
> ip address 10.10.10.10 255.255.255.255
> !
> interface Tunnel12
> no ip address
> ipv6 address 2001:12:12:12::1/64
> tunnel source Loopback0
> tunnel destination 10.20.20.20
> [tunnel mode gre ip] <- replace later with "tunnel mode ipv6ip"
> !
>
> R2:
> interface Loopback0
> ip address 10.20.20.20 255.255.255.255
> !
> interface Tunnel12
> no ip address
> ipv6 address 2001:12:12:12::2/64
> tunnel source Loopback0
> tunnel destination 10.10.10.10
> [tunnel mode gre ip] <- default (therefore won't show)
>
>
> -
> Daniel
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> Of
> Scott Morris
> Sent: Sonntag, 8. Mdrz 2009 14:23
> To: 'GAURAV MADAN'; 'Modular'
> Cc: 'Cisco certification'
> Subject: RE: IPV6 Tunnels...
>
> The pro/con I'd look at is overall packet size.
>
> IPv6IP you have a 40-byte IPv6 header + 20-byte IP header
>
> GRE you have a 40-byte IPv6 header + 8 byte GRE header + 20 byte IP
> header
>
> Which is smaller?
>
> Scott
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> Of
> GAURAV MADAN
> Sent: Sunday, March 08, 2009 7:18 AM
> To: Modular
> Cc: Cisco certification
> Subject: Re: IPV6 Tunnels...
>
> No pros / cons as such .. but sometimes language of ques can make us
> go mad
>
> protocol 47 : GRE
> protocol 41 : IPV6IP
>
> I rememebr these 2 numbers always and can be useful in desiging ACLs
> as well
>
>
> Gaurav Madan.
>
> On Sun, Mar 8, 2009 at 4:37 AM, Modular <modulartx@gmail.com> wrote:
>
>> So I've learned that if you want to tunnel IPv6 over IPv4, there
>> are two
>> easy options you can turn to.
>>
>> 1. Normal GRE tunnel, using the default tunnel type.
>>
>> 2. Configuring ipv6ip tunnel type.
>>
>> What are the pros/cons of using each?
>>
>> Thanks,
>> Mod...
>>
>>
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>>
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>
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>
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