Just A Little Explanation....

Why is it that I can still access the SM on its default IP address 169.254.1.1 eventhough my PC got a diffrent IP subnet already? My PC got DHCP IP from a server, say on the subnet of 192.168.x.x. Canopy SM is just configured to associate with the AP. Its IP is still set to its default state and Network Accessibility is on Local. I can browse the net and access Canopy at the same time. I just need a little explanation on this. Is this something to do with the Canopy SM being a Layer 2 device? If that’s the answer, how? I am just 5x5 when it comes to technicalities.:roll:

I have thought about this from time to time also. Here is what I came up with.

Our SM’s are on 192.168.0.0/24. All SM’s are in Bridge Mode and terminate into WAN Ports of SOHO routers. The SOHO routers are doing NAT. The LAN interface address of the SOHO router is usually 192.168.1.1. PC’s on that LAN are 192.168.1.0/24.

If I enter, say 192.168.0.254 in a browser from a PC on the LAN, that packet is going to be forwaded to the default gateway, 192.168.1.1. That router will query its routing table, and since there is no static route to 192.168.0.0/24, it will forward the packet via the default route, which is to the IP address of the edge router connected to the Internet. The first hop to this path is through the SM.

So, my guess is that as soon as it hits the SM, the SM says, “hey, that’s me”, and the Web Interface pops up.

mmm… never come across this but that doesn’t make sense… the last hop is done via MAC address and not IP…

when the SOHO router decides to forward the packed to the default IP (edge router) it looks up the MAC address of that IP and then send the packet to that MAC address (the canopy, BH, or any other switches have a MAC address table/Bridge table that tells them which port to forward the packet to for that MAC address).

what is the gateway IP on the SM and where does that gateway reside ?

Hi,

New member first post.

I had conducted few tests regarding this issue.

My PC (sameat) : ip 202.79.55.249/24 gw 202.79.55.9
directly connected to
My SM: ip 172.16.55.249/16 gw 172.16.55.9 , Network access. Local

Test from my PC.

samit@sameat ~ $ ping 172.16.55.249
PING 172.16.55.249 (172.16.55.249) 56(84) bytes of data.
64 bytes from 172.16.55.249: icmp_seq=1 ttl=255 time=2.01 ms
64 bytes from 172.16.55.249: icmp_seq=2 ttl=255 time=2.06 ms
64 bytes from 172.16.55.249: icmp_seq=3 ttl=255 time=2.33 ms

samit@sameat ~ $ traceroute 172.16.55.249
traceroute to 172.16.55.249 (172.16.55.249), 30 hops max, 38 byte packets
1 172.16.55.249 (172.16.55.249) 7.912 ms 13.787 ms 3.091 ms
samit@sameat ~ $

The delay 2ms in ping and 1 hops in traceroute means no gateway involved in communication between PC and SM.

To verifiy I tcpdump in my gateway 202.79.55.9 having Ethernet alias 172.16.55.9 ie same machine. No packets received at all.

Finally I tcpdump in My PC with -e options:

sameat ~ # tcpdump -i ath0 -nn -e net 202.79.55.249 and net 172.16.55.249

tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on ath0, link-type EN10MB (Ethernet), capture size 96 bytes
12:16:07.480477 00:14:a4:08:af:de > 00:01:02:63:15:24, ethertype IPv4 (0x0800), length 98: 202.79.55.249 > 172.16.55.249: ICMP echo request, id 49684, seq 80, length 64
12:16:07.483062 1a:00:3e:00:a7:c4 > 00:14:a4:08:af:de, ethertype IPv4 (0x0800), length 98: 172.16.55.249 > 202.79.55.249: ICMP echo reply, id 49684, seq 80, length 64


I saw request sent to 00:01:02:63:15:24 which mac address of my default gw 202.79.55.9, which is correct.
ooops…
but reply coming from 1a:00:3e:00:a7:c4 which is mac address of SM .

This suggest me that SM is spoofing the packet destinate to its IP 172.16.55.249 and sending the reply.

page 159/160 in release 8 doc may help explain how the management interface is implemented in Canopy

Here’s my setup…My SM is directly connected to my PC and is associated to an AP on a BTS. BTS gives DHCP IP subnet on 192 series (of course there are still other hops to go to WWW). Eventhough I put other IP subnet in my SM, as long as the Network Accessibility is on Local, I can still see its GUI (and browse the net at the same time). When I put a SOHO router behind my SM, I can’t do what I do on my first setup…that’s logical…request is passing through a NAT device, that explains it. Anyway, I duplicated the setup…a bit. I made a WLAN using AP and SM. A SOHO router is connected to AP and my PC to SM…no internet connection…just WLAN. SOHO router gives DHCP IP subnet to my PC though AP-SM connectivity. I put a 10 series IP subnet on my SM and Network Accessibilty is on Local. Now, I can see the SOHO router and SM’s GUI page at the same time. For me, that’s not logical…

If someone could explain this one. I’m hoping for a logical answer…hehehehe! :roll:

you’re a smart bro subscriber?

simple… sm only acts as a bridge…