>> It can be done, but 1) it means that it's possible for hosts on RFC1918 >> addresses to reach the routable addresses directly without going via the >> router and vice-versa (which may or may not be a problem), 2) you'll >> need to think about how you want to arrange things if you use DHCP, and >> 3) it complicates things for firewall and nat rules. > > 1. I do not believe this should be a problem, as far as I am aware this > is routed based on MAC address (Layer 2), but IP addresses are a higher > layer (Layer 3).
It means that your directly internet-accessible hosts have a way that they can reach your internal-network hosts without going through the firewall. Many network admins would consider this a problem. > 2. DHCP is simple, it is only for the private block (192.168.2.1/24) > which devices will use by default, global addresses from the /29 block > is assigned manually, this is because most containers are internal, > which the NAT is just so they can still access the internet, but not > expose themself fully (and before you say "why not use a global > address" that's fine, you have thought about how to arrange things for this > IPv4 addresses are expensive and I am lucky to have a /29, fwiw, you're using an expensive ISP which has ample spare addresses, there's a faorly good chance they'll give you more if asked. > 3. I don't think so, because I specify the "from" address as either from > 192.168.2.1/24 or the static block, which clearly distinguishes between > them. Also the "quick" rules are above the NAT, this should pick up and > pass out the traffic respectively before it even gets to NAT, I doubt > this is the issue and I believe it lies within the routing table. it's common to be able to use the network interface on which a packet is received as part of the decision whether to accept that packet. most example rulesets you'll find do that, so be aware if cribbing from other setups. >> 217.169.18.56 is a network address (mask it out against the netmask, >> the remaining "host bits" are all zeroes), you cannot use this (or the >> broadcast address) as a host address >> >> $ ipcalc 217.169.18.56/29 >> address : 217.169.18.56 >> netmask : 255.255.255.248 (0xfffffff8) >> network : 217.169.18.56 /29 >> broadcast : 217.169.18.63 >> host min : 217.169.18.57 >> host max : 217.169.18.62 >> hosts/net : 6 > > Ah my mistake, I totally forgot about the loopback address which would > be 217.169.18.56, this is from my own stupidity. > t's not a loopback, it's the network address. > But in theory, can I assign IPs from the /29 without having a default > gateway from that block, could I put the gateway as the /32 and keep all > 6 of the usable IPv4s? > > A router does not need 2 IPv4's, only one, so is it possible to keep one > or is it a requirement to have an IPv4 from the block assigned to the > router? hosts within that subnet need to be able to send ethernet paclets that reach the router. this is normally done by ARP which requires that the router has a host address (not a network or broadcast address) within the subnet. there are other ways to do it but they are fiddly, more fragile (requiring changes on every host if the router hardwarw address is changed), and really not recommended to go down that route unless you have a solid grasp of the basics. > > But the fact remains is, I believe all the addresses are bound to by the > router not according to what you've shown in your mail. > nmap'ing all the IPv4s in the block return the ports open by the > router. there's going to be some reason for this but it'll be easier to fix what's obviously a problem first and then go from there. > So it should be: > > inet alias 217.169.18.57 255.255.255.248 217.169.18.63 > > correct? yes, or you can leave off the broadcast address, it's set by default anyway. (remember to renumber the existing .57 host if you're going to use .57 for the router) -- Please keep replies on the mailing list.
