On 7/6/10 8:01 AM, Stephen Brown wrote:
> I am thinking about signing up for Comcast Business class internet with
> 5 public IP's.
> 
> I run a shorewall box with two network cards, and no space to add any
> more. eth0 is currently pointing towards my existing DSL provider (with
> a single IP) and eth1 is NAT'ed and pointed towards my small home network.
> 
> What would be the best practice to deal with this scenario? The first
> thoughts that come to mind is to setup virtual interaces (eg. eth0:0,
> eth0:1, etc) and assign them to the net zone along with a respective IP
> from Comcast.

You need to read
http://www.shorewall.net/Shorewall_and_Aliased_Interfaces.html. You do
not define aliased interfaces to Shorewall.

> 
> I'm waiting to hear back from Comcast on the brand and type of
> firewall/modem they will be installing, but they have said it is able to
> be bridged, I'd just like to know if I can deal with all 5 IP's with one
> interface on the Shorewall side...

I have Comcast Business class service. What you get is a 'Comcast
Business Gateway' which is a router with built-in firewall, NAT, DHCP,
etc. I did not get a manual for this thing and had a hell of a time
finding one on the Comcast Business Class web site. By the time that I
did find the PDF to download, I had already muddled through and arrived
at the same solution that the manual recommends:

1. The default internal network is 10.1.10.0/24 with the gateway having
address 10.1.10.1/24; I left it that way.
2. I modified the DHCP server configuration on the business gateway to
not assign 10.1.10.2 - 10.1.10.19.
3. I configured my Shorewall box's external interface as 10.1.10.11/24.
4. On the business gateway, I added a static route to my /29
(70.90.191.120/29) via 10.1.10.11.
5. I configured the business gateway's firewall to not filter traffic to
the /29 (there's a check-box for that, IIRC).
6. I run Linux-vserver on my Shorewall box so I configure the public IP
addresses on the box's external interface (3 statically configured and
two are dynamically configured when I start my vservers). Here are my
/etc/shorewall/interfaces stanzas:

#
# Commcast Business Class
#
auto eth1 eth1:1 eth1:2 eth1:3
iface eth1 inet static
        address 70.90.191.121
        netmask 255.255.255.248
        network 70.90.191.120
        broadcast 70.90.191.127
        gateway 70.90.191.126

iface eth1:1 inet static
        address 70.90.191.122
        netmask 255.255.255.248
        network 70.90.191.120
        broadcast 70.90.191.127

iface eth1:2 inet static
        address 70.90.191.123
        netmask 255.255.255.248
        network 70.90.191.120
        broadcast 70.90.191.127

iface eth1:3 inet static
        address 10.1.10.11
        netmask 255.255.255.0
        network 10.1.10.0
        broadcast 10.1.10.255

The business class gateway has public IP address 60.90.191.126 so that's
what I configure as the Shorewall box's default gateway.

Here's the config up and running:

gateway:~# ip -4 addr ls dev eth1
3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast
state UNKNOWN qlen 1000
    inet 70.90.191.121/29 brd 70.90.191.127 scope global eth1
    inet 10.1.10.11/24 brd 10.1.10.255 scope global eth1:3
    inet 70.90.191.122/29 brd 70.90.191.127 scope global secondary eth1:1
    inet 70.90.191.123/29 brd 70.90.191.127 scope global secondary eth1:2
    inet 70.90.191.124/29 brd 70.90.191.127 scope global secondary eth1
    inet 70.90.191.125/29 brd 70.90.191.127 scope global secondary eth1
gateway:~#

My Shorewall configuration just has:

/etc/shorewall/interfaces:

net    COMCAST    detect  physical=eth1,...

/etc/shorewall/masq:

#INTERFACE                      SOURCE                  ADDRESS

COMMENT Masquerade Local Network

COMCAST:10.1.10.0/24            0.0.0.0/0               10.1.10.11
COMCAST                         !70.90.191.120/29       70.90.191.122

gateway:~#

By leaving the DHCP server running on the Business Class Gateway, I can
plug my wireless access point and work system into the gateway's
built-in switch when I want to take the Shorewall box down for
maintenance; that way, I can maintain internet access for work and for
our in-home wireless network.

Hope this helps.
-Tom




-- 
Tom Eastep        \ When I die, I want to go like my Grandfather who
Shoreline,         \ died peacefully in his sleep. Not screaming like
Washington, USA     \ all of the passengers in his car
http://shorewall.net \________________________________________________

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