How to make a small Linux firewall for cable modem(s)

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Using a development version – https://www.ubuntu.com/download/server an Linux server makes a good companion. To monitor the upstream service provider, or simply to secure resources that belong to a different network segment than the internet router.

If you already have a Linux server running with your cable modem device, check this command:


tcpdump -i fxp0 -nN -vvv -xX -s 1500 > fat_globules

Spiders and nasty things can really be a pain. – Especially when they belong to you. Please do:

vi fat_globules

Inside of this file is something only a mesusse would know. It appears to be very very elaborate; containing all sorts of connections made by your PC. There are flat ones like arp requests, and strange connections to an idle computer. Yours.

So, knowing that; what did it have in mind? –

We don’t know. The idea is however, if they stay there; they can cause trouble. – But if they go with the Linux server its self – well then. Thats actually not a big deal at all. To some. – arf

Strange things happen with using a Linux server for this purpose, in that it is not necessary to explain most things. – But they do if they are not the default set of options – but input vectors on a median.

You really really dont want a median curve, when designing the difference. Taking the difference of using the linux firewall is subjective. –

For example vonage telephone Voip equipment may not have the operations necessary to compute it. – what else will what do. – suddenly.

I dont really care to know; but for several reasons.

  1. where is the killing eye?
  2. What do you expect to happen if this configuration fails to compute a basic mmorpg video game?
  3. What if the equipment its self fails to negotiate with something more important – like your modis?

There are actually serious medical conditions with the same address. So, let’s not worry about that just yet. First you do; actually have an address. Its a big step that some people miss. What is all this mail sent to me all of the sudden. Again, since we have no idea then it would be good to purchase a lame old computer to do this. every day. it stacks up.

It keeps going. Also, laudably until it completes its investigation of the material. Which sometimes is never. In the middle of the desert. Yes; sell all your network equipment to the poor. No kidding here. yikes.

Some of it would not even appear to work – until its turned on or set up. Or more simply the purpose of its operation is for the religious. You cant do anything about it. And there is really no answer for it. The changes I see are not the purpose of its operation. – And Maybe not that computer altogether. – Really not that computer.

Maybe the library. So you dont – want to read anything?

Anyway, a linux server checks to see what network equipment is installed when it boots. What is it booting – the development version knows – maybe.

So, carefully install two network cards. The two network cards used will either work or not work for whatever reason. Your reason – in your own reasoning. – That you cant get back – ever. In front of other people who can see your sebaceous cantor – unable to explain yourself. You dont really know any celebrities. Except maybe yourself –

Anyway, obviously some people dont like kinds of music -they dont like red-hair music – or you in general. – turn into a pretzel. Problem solved.

Although the network device may not appear to be there:

ifconfig -a | more

will tell you what it is. No problem there – at least for the first week. yikes. Avoid this whole area. A genius once summed this up in 5 words.

get – the – little – boy -out.

Nice. Rather than figuring this out, for yourself:

root@ubuntu:/var/log# ifconfig -a
enp1s1: flags=4163 mtu 1500
inet 192.168.0.1 netmask 255.255.255.0 broadcast 192.168.0.255
inet6 fe80::290:27ff:feac:9085 prefixlen 64 scopeid 0x20
ether 00:90:27:ac:90:85 txqueuelen 1000 (Ethernet)
RX packets 2046216 bytes 316134285 (316.1 MB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 3045348 bytes 3333065010 (3.3 GB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

enp1s8: flags=4163 mtu 1500
inet 10.0.0.112 netmask 255.255.255.0 broadcast 10.0.0.255
inet6 2601:144:100:9d2c:20c:f1ff:fe92:54f1 prefixlen 64 scopeid 0x0
inet6 fe80::20c:f1ff:fe92:54f1 prefixlen 64 scopeid 0x20
ether 00:0c:f1:92:54:f1 txqueuelen 1000 (Ethernet)
RX packets 3083611 bytes 3385101907 (3.3 GB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 2079452 bytes 304972082 (304.9 MB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

lo: flags=73 mtu 65536
inet 127.0.0.1 netmask 255.0.0.0
inet6 ::1 prefixlen 128 scopeid 0x10
loop txqueuelen 1000 (Local Loopback)
RX packets 80963 bytes 13969256 (13.9 MB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 80963 bytes 13969256 (13.9 MB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

Now run the dchp client to the internet router –

dhclient -v enp1s8

assign an address to the second network card:

ifconfig enp1s1 192.168.0.1 netmask 255.255.255.0

apply ip masquerade:

iptables -t nat -A POSTROUTING -s 192.168.0.1/24 ! -d 192.168.0.1/24 -j MASQUERADE

make sure that you can successfully connect to it:

iptables -A INPUT -p tcp –dport 22 -m tcp -j ACCEPT

Thats it! – now your working in the mines.

tcp/ip v4



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