On Thu, May 10, 2012 at 2:54 AM, Phil Mayers <p.may...@imperial.ac.uk>wrote:
> On 09/05/12 22:55, Jonathan Lassoff wrote:
>
> I've gotten this to work in the past, but it ended up being a LOT more
>> work
>> than just using DNS names and routing (which I've subsequently done each
>> time).
>>
>
> Out of curiosity, how did this work? Isn't most mDNS traffic TTL=1?
I don't know about all the various implementations out there (of if the
standard says anything), but my modern-ish OSX box does 255:
v6:
Internet Protocol Version 6, Src: fe80::xxxx:xxff:xxxx:xxxx
(fe80::xxxx:xxff:xxxx:xxxx), Dst: ff02::fb (ff02::fb)
0110 .... = Version: 6
[0110 .... = This field makes the filter "ip.version == 6"
possible: 6]
.... 0000 0000 .... .... .... .... .... = Traffic class: 0x00000000
.... 0000 00.. .... .... .... .... .... = Differentiated
Services Field: Default (0x00000000)
.... .... ..0. .... .... .... .... .... = ECN-Capable Transport
(ECT): Not set
.... .... ...0 .... .... .... .... .... = ECN-CE: Not set
.... .... .... 0000 0000 0000 0000 0000 = Flowlabel: 0x00000000
Payload length: 35
Next header: UDP (0x11)
Hop limit: 255
Source: fe80::xxxx:xxff:xxxx:xxxx (fe80::xxxx:xxff:xxxx:xxxx)
[Source SA MAC: xx:xx:xx:xx:xx:xx (xx:xx:xx:xx:xx:xx)]
Destination: ff02::fb (ff02::fb)
User Datagram Protocol, Src Port: 5353 (5353), Dst Port: 5353 (5353)
Source port: 5353 (5353)
Destination port: 5353 (5353)
Length: 35
Checksum: 0x4aa1 [validation disabled]
[Good Checksum: False]
[Bad Checksum: False]
Domain Name System (query)
......
and the v4 case:
Ethernet II, Src: xx:xx:xx:xx:xx:xx (xx:xx:xx:xx:xx:xx), Dst:
01:00:5e:00:00:fb (01:00:5e:00:00:fb)
Destination: 01:00:5e:00:00:fb (01:00:5e:00:00:fb)
Address: 01:00:5e:00:00:fb (01:00:5e:00:00:fb)
.... ...1 .... .... .... .... = IG bit: Group address
(multicast/broadcast)
.... ..0. .... .... .... .... = LG bit: Globally unique address
(factory default)
Source: xx:xx:xx:xx:xx:xx (xx:xx:xx:xx:xx:xx)
Address: xx:xx:xx:xx:xx:xx (xx:xx:xx:xx:xx:xx)
.... ...0 .... .... .... .... = IG bit: Individual address
(unicast)
.... ..0. .... .... .... .... = LG bit: Globally unique address
(factory default)
Type: IP (0x0800)
Internet Protocol Version 4, Src: nn.nn.nn.nn (nn.nn.nn.nn), Dst:
224.0.0.251 (224.0.0.251)
Version: 4
Header length: 20 bytes
Differentiated Services Field: 0x00 (DSCP 0x00: Default; ECN: 0x00:
Not-ECT (Not ECN-Capable Transport))
0000 00.. = Differentiated Services Codepoint: Default (0x00)
.... ..00 = Explicit Congestion Notification: Not-ECT (Not
ECN-Capable Transport) (0x00)
Total Length: 55
Identification: 0xd6ca (54986)
Flags: 0x00
0... .... = Reserved bit: Not set
.0.. .... = Don't fragment: Not set
..0. .... = More fragments: Not set
Fragment offset: 0
Time to live: 255
Protocol: UDP (17)
Header checksum: 0x82ad [correct]
[Good: True]
[Bad: False]
Source: nn.nn.nn.nn (nn.nn.nn.nn)
Destination: 224.0.0.251 (224.0.0.251)
User Datagram Protocol, Src Port: 5353 (5353), Dst Port: 5353 (5353)
Source port: 5353 (5353)
Destination port: 5353 (5353)
Length: 35
Checksum: 0x2886 [validation disabled]
[Good Checksum: False]
[Bad Checksum: False]
Domain Name System (query)
....
Cheers,
jof
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