[ALUG] Firewall log entry

steve-ALUG at hst.me.uk steve-ALUG at hst.me.uk
Tue Jan 26 10:31:34 GMT 2016


On 26/01/16 09:32, James Bensley wrote:
> On 26 January 2016 at 09:11,  <steve-ALUG at hst.me.uk> wrote:
>> Hi y'all!
>> I'm confuzzled.
>>
>> I have repeated entries in my syslog in log file viewer.
>>
>>
>> Jan 26 08:31:42 MYSERV kernel: [25624.013276] [UFW BLOCK] IN=eth0 OUT=
>> MAC=BIG_MAC SRC=192.168.1.1 DST=224.0.0.1 LEN=28 TOS=0x00 PREC=0x00 TTL=1
>> ID=0 PROTO=2

>> Where MYSERV is the name of my server, and
>> BIG_MAC is what appears to be a mac address but longer than I am used to .
>> always the same number, =01:00:5e:00:00:01:a0:21:b7:43:91:37:08:00
> For some reason it looks like your syslog server is not "chopping up
> the data" at the correct boundaries;
>
> 01:00:5e:00:00:01 is the destination MAC address this Ethernet frame
> is being sent to which is a multicast MAC address, which ties up with
> the fact that the destination IP address is 224.0.0.1 which is a
> multicast IP address. a0:21:b7:43:91:37 is the source MAC address of
> this Ethernet frame which according to http://www.macvendorlookup.com/
> is a Netgear MAC address, do you have any Netgear equipment at home?
> 08:00 on the end is probably the Ethertype value which comes directly
> after the source and destination MAC address in an Ethernet frame
> header, 0x0800 means an IP packet is contained within this Ethernet
> frame.
>
> So it seems perhaps you have a netgear router and it's sending out
> multicast IP packets to your LAN looking for something/someone (it
> could be IGMP is turned on by default and in such case, it's nothing
> to worrie about). You'd need to run tcpdump or Wireshark to capture
> the full packet to see what it's looking for.
>
> Hope that helps,
> James.
>
>

It does.  Thanks.  There is (I think) a router manufactured by Netgear. 
  I'll do a capture at some later time.  I'm still confused over why 
it's using 192.168.1.1 though as it's configured to (and is) using 
192.168.0.1.


Thanks for your help.
Steve



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