Here is my situation, I have a router R1 whose external IP address is 11.11.2.1. I have another router R2 whose external IP address is 5.5.2.1.
I am running eBGP on R1 and R2. However, I cannot ping R2 from R1 and R1 from R2. How can I make them to ping each other? I know that they are in a different subnet. But, this can be a practical case where I don't want to force the external IP address to match the subnet of the other router interface.
I have never worked on the customer premises, but my assumption is that one service provider runs IGP services internally - For example - OSPF or IS-IS. Now, when one service provider has to reach another service provider to communicate server on the third service provider, it will pass/transit through another ISP.
In my example - ISP-2. My question is -
Apart from multiple OSPF area's, which is to limit 50 routers per area, is it really the way internet works. You can ignore the fact that it can be IS-IS or other igp protocols within AS. In simple words, is this a kind of real topology of internet.
Next, my context based question is if this is the typical scenario, then how I can ping 11.11.11.11 from R2.
I am saying this because -
AS-100 has all their internal route information -- OSPF 1 -- it doesn't know how to reach 11.11.11.11
AS -200 has all their internal route information - OSPF 2
AS -300 has all their internal route information - OSPF 3
I have connected AS 100 with AS 200 using EBGP. Similarly, AS 200 with AS-300 . This I have done using neighbor command.
Questions -
Do I need to advertise each and every network information of ISP-2 to ISP1 and ISP-3 so that they all can communicate? If so, is it done in the same way in the real network. This will be such a tiring job to advertise each and every network information of ISPs. How can I do this automatically? I am using CISCO - GNS3 any cisco commands will help. I have explored re-distribute but I haven't understood much. Also, in the real network - if you advertise each and every routing information to other ISPs then the routing table will become so large. Do we normally do this? But, I believe if we don't do so then how can I communicate to internal network of other ISPs. So, I believe we have to do so. This means routing table will be very large. Am I correct here?
I am trying to learn computer networking by experimenting on cisco packet tracer. Here is what I have done, but I see that I cannot create a static route for it. The cisco packet tracer throws error -
Router(config)#ip route 192.168.2.0 255.255.255.0 192.168.2.101
%Invalid next hop address (it's this router)
I can't see that I can assign IP address to a switch.
Here is the topology.
I am using fedora core machine. My linux- fedora core machine - client wants to send the dhcp option 60 specifying the vendor id to the dhcp server. Next, I want to read the dhcp option 43 send by the server. Already, I know that the dhcp server is configured properly. How can I do so? I tried doing google, but majority of the articles are on the server side configuration.
I have a linux Fedora -16 machine that has two interfaces -
em1 Link encap:Ethernet HWaddr B8:CA:3A:89:EE:F1
inet addr:136.170.195.17 Bcast:136.170.195.255 Mask:255.255.252.0
inet6 addr: fec0::f:baca:3aff:fe89:eef1/64 Scope:Site
inet6 addr: 2002:88aa:c268:f:baca:3aff:fe89:eef1/64 Scope:Global
inet6 addr: fe80::baca:3aff:fe89:eef1/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:6363373 errors:0 dropped:2 overruns:0 frame:0
TX packets:1571017 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:4502189587 (4.1 GiB) TX bytes:175801460 (167.6 MiB)
Interrupt:20 Memory:f7f00000-f7f20000
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:765 errors:0 dropped:0 overruns:0 frame:0
TX packets:765 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:85089 (83.0 KiB) TX bytes:85089 (83.0 KiB)
p3p1 Link encap:Ethernet HWaddr 14:D6:4D:1F:F3:F8
inet addr:10.240.100.110 Bcast:10.240.100.255 Mask:255.255.255.0
inet6 addr: fe80::16d6:4dff:fe1f:f3f8/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:2615351 errors:0 dropped:0 overruns:0 frame:0
TX packets:2868133 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:1081785835 (1.0 GiB) TX bytes:1577912608 (1.4 GiB)
On the interface p3p1, I am running a dhcp server. My embedded device, which runs on a NFS, gets the IP address from p3p1. The p3p1 interface is connected to my embedded device - Point to Point.
Now, from the embedded box ( a linux based system), I want to ping/access the address - 136.170.195.17.
I cannot do the following because, the gw doesn't know how to route the packets for 136.170.0.0 subnet. So, I get an error -
# ping 136.170.195.17
PING 136.170.195.17 (136.170.195.17): 56 data bytes
ping: sendto: Network is unreachable
Since the communication is on the different network, I need to add the route in the device. So, what I have done is enabled the packet forwarding in my linux machine. Next, I have add the route like this.
# /sbin/route add net 136.170.192.0 netmask 255.255.252.0 gw 10.240.100.110
route: resolving net
I am getting the above error. I think that my understanding of network is not in-correct. What is the reason that I am getting the following error? Actually, I am baffled with the above error. In my opinion, there is nothing wrong in my concepts like - enabling packet forwarding and adding the route for the packet destined for the different subnet. Because for the same subnet, the route doesn't come into the picture - it is just based on ARP. How can I fix this issue? Is there any problem in my understanding?
Here is the box routing table -
# netstat -anr
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
10.240.100.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
Here is my PC routing table -
$ netstat -arn
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
0.0.0.0 136.170.192.2 0.0.0.0 UG 0 0 0 em1
10.240.100.0 0.0.0.0 255.255.255.0 U 0 0 0 p3p1
136.170.192.0 0.0.0.0 255.255.252.0 U 0 0 0 em1
169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 p3p1
I have referred to the following links before asking this question.
I am making an example for my students on NAT - pre-routing. Here, I am trying to replace the destination ip with the one I want. For example, when someone tries to access www.facebook.com, the wwww.google.com will be connected.
Here is what I have tried to do.
# host www.facebook.com
www.facebook.com is an alias for star.c10r.facebook.com.
star.c10r.facebook.com has address 31.13.79.65
star.c10r.facebook.com has IPv6 address 2a03:2880:f002:201:face:b00c:0:1
^C[root@shreyas joshis1]#
# host www.google.com
www.google.com has address 74.125.236.81
www.google.com has IPv6 address 2404:6800:4001:802::1014
[root@shreyas joshis1]#
Now, here is the IP table rule.
# iptables -t nat -I PREROUTING -p tcp --dport 80 -d 31.13.79.65 -j DNAT --to-destination 74.125.236.81
# iptables -t nat -I PREROUTING -p tcp --dport 443 -d 31.13.79.65 -j DNAT --to-destination 74.125.236.81
Now, commit to the table.
# iptables-save
However, it doesn't work. One thing I know that the DNS resolution can happen to multiple IP's based on the region,etc. Because these sites have DNS load balancer.
The thing is that I can block these IP's. I believe that iptables works on the network layer. Thus, the HTTP request should have come to this layer. On reaching this layer, it should have pre-routed to the other IP. For example, whenever the IP destination is 31.13.79.65, change it to the destination IP - 74.125.236.81.
Thus, after DNS resolution, if the browser will request anything for the IP 31.13.79.65, the network layer should change it to 74.125.236.81. However, it doesn't work. Can somebody please explain why?
Please bear in mind that I am not an expert in networking. I have tried my best to put up the best of the knowledge I have on networking.