>> I did try to execute a ping on the same network topology H1 (10.0.1.2)---> >> H4(10.0.2.2) using the simple L3 switch in POX, however I could only see ARP >> requests from H1 to S2. I don't see the reply being sent. I am not sure >> where I am going wrong..
You're seeing the ARPs for 10.0.1.1 -- but that's not really S2 in any real sense. There's not really such a thing as 10.0.1.1. The switch is not a router. And that's the problem you're seeing with POX's l3_learning -- the gateways. 10.0.1.1 and 10.0.2.1 don't exist. If you just omitted the gateways (as if you were on a giant 0.0.0.0 "subnet"), it should work fine, because in this case, 10.0.1.2 would just ARP for 10.0.2.2, which should work. Then 10.0.1.2 would get a MAC, which would be 10.0.2.2 itself, send there, and that would work. The version of l3_learning in my public POX fork on github (which will eventually be getting merged upstream) handles the case of gateways by setting up "fakeways" (e.g., it can be set to do fake ARP replies for arbitrary IP addresses), and by always rewriting destination MACs (to change them from the gateway MACs to the actual destination MACs). (There was recently some discussion about l3_learning on pox-dev that discusses this more.) If you want to keep debugging your NOX app, I'd suggest that you sniff the traffic between s3 and h4. Verify that the echo request shows up there coming from the switch. Then see what follows that coming from h4. -- Murphy On Jul 23, 2012, at 9:35 AM, Rashmi Pujar wrote: > The network topology that i configured in Mininet is as below. Each host was > configured with a default gateway. > > h1<-->s2<-->s3<-->h4 > > h1 ifconfig h1-eth0 10.0.1.2/24 > h4 ifconfig h4-eth0 10.0.2.2/24 > h1 route add default gw 10.0.1.1 > h4 route add default gw 10.0.2.1 > > and i tried to run: h1 ping -c1 h4 > > - Rashmi > > > On Sun, Jul 22, 2012 at 11:47 PM, Murphy McCauley <[email protected]> > wrote: > (Copying pox-dev) > > You mention both 10.0.2.2 and 10.0.1.2. Which is it? Did you use the right > one when testing? > > Also, can you explain exactly how you configured and started up Mininet? > > -- Murphy > > On Jul 19, 2012, at 5:28 PM, Rashmi Pujar wrote: > >> I am a newbie to Openflow and I have been using the Openflow tutorial and >> the VM image that comes along to get myself started....and hence continued >> to use NOX >> >> To monitor the OF traffic between the controller and switch I used Wireshary >> and the last OF traffic i saw was a OFP+ICMP Packet-In for H1--->H4 from >> Switch3 port to Controller Port.. >> For ARP requests sent from hosts to switches, I build an ARP reply to be >> sent to the host. I can see OFP+ARP packet-in and out in Wireshark. >> >> I did try to execute a ping on the same network topology H1 (10.0.1.2)---> >> H4(10.0.2.2) using the simple L3 switch in POX, however I could only see ARP >> requests from H1 to S2. I don't see the reply being sent. I am not sure >> where I am going wrong.. >> >> DEBUG:forwarding.l3_learning:2 1 flooding ARP request 10.0.1.2 => 10.0.1.1 >> DEBUG:forwarding.l3_learning:3 1 ARP request 10.0.1.2 => 10.0.1.1 >> DEBUG:forwarding.l3_learning:3 1 flooding ARP request 10.0.1.2 => 10.0.1.1 >> DEBUG:forwarding.l3_learning:2 1 ARP request 10.0.1.2 => 10.0.1.1 >> DEBUG:forwarding.l3_learning:2 1 flooding ARP request 10.0.1.2 => 10.0.1.1 >> DEBUG:forwarding.l3_learning:3 1 ARP request 10.0.1.2 => 10.0.1.1 >> DEBUG:forwarding.l3_learning:3 1 flooding ARP request 10.0.1.2 => 10.0.1.1 >> DEBUG:forwarding.l3_learning:2 1 ARP request 10.0.1.2 => 10.0.1.1 >> DEBUG:forwarding.l3_learning:2 1 flooding ARP request 10.0.1.2 => 10.0.1.1 >> DEBUG:forwarding.l3_learning:3 1 ARP request 10.0.1.2 => 10.0.1.1 >> DEBUG:forwarding.l3_learning:3 1 flooding ARP request 10.0.1.2 => 10.0.1.1 >> >> - Rashmi >> >> >> On Thu, Jul 19, 2012 at 4:55 PM, Murphy McCauley <[email protected]> >> wrote: >> Do you have a good reason for using NOX-Classic? As we're no longer doing >> any development with it, you might think about using POX (which already >> contains a simple L3 switch). >> >> To more directly answer your question, you can use Wireshark to monitor the >> OpenFlow traffic between the controller and the switch. The OpenFlow >> reference implementation contains the OpenFlow dissector, and there's also a >> github project for it. >> >> What are you doing about non-IP traffic? More to the point, what are you >> doing about ARP? >> >> -- Murphy >> >> On Jul 19, 2012, at 4:46 PM, Rashmi Pujar wrote: >> >> > Hi, >> > I am trying to implement a static L3 Switch using NOX in Python. I have >> > hardcoded the IPs and hence I do not perform any 'IP learning' as such. >> > My network topology looks as below. >> > >> > Switch2<---------->Switch3 >> > | | >> > | | >> > H1 H4 >> > >> > When Host1 tries to ping H4 i.e. an ICMP req to H4. The controller ensures >> > the destination mac address in this request is that of H4's; installs a >> > flow in Switch2 and forwards the packet to the next hop i.e. Switch3. At >> > Switch3 the arriving ICMP req has no flow entry and hence is sent to >> > controller. The controller again checks against its IP table and installs >> > a flow in Switch3 to finally forward the packet to the host at H4. I can >> > see in my logs that a flow entry is being made for action on an >> > appropriate port connecting to H4. However, I am expecting an ICMP echo >> > reply from H4 to complete the ping process and I do not see that >> > happenening...Is there a way to debug this, to actually see if an OF >> > packet has been sent to the host at H4? Am I expected to handle ICMP >> > requests? >> > >> > It would be great if you could help. >> > >> > Thanks, >> > Rashmi >> > >> >> > >
