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8 votes
Accepted

Configuring OSPF on two directly connected routers which are in different areas

In order to connect two areas, one router has to serve as an area border router (ABR). That router has interfaces in both areas. In other words, the boundary between two areas is a router, not the ...
Ron Trunk's user avatar
  • 67.6k
7 votes

How to run a CAM Table Overflow attack in GNS3 using Cisco 3725 routers?

First and foremost, I must indicate that I am mostly active on the IT Security StackExchange website. Since this current website may reach a different public I find it wiser to tell that, while I ...
WhiteWinterWolf's user avatar
7 votes
Accepted

GNS3 switches vs Real switches performance

Do emulated switches perform worst than actual switches? Yes, of course software performs worse than hardware. Physical switches do their switching in hardware, and are able the get wirespeed ...
Ron Maupin's user avatar
  • 99.8k
6 votes
Accepted

Should a PC populate its ARP table when a frame is not destined to it?

Yes, this is expected behaviour. Even though PC3 sees the ARP request from PC1, it does not populate it's ARP cache with the IP-to-MAC mapping of PC1. While this may not seem to be the most efficient ...
Benjamin Dale's user avatar
6 votes

Why switch has records in mac-table when i just set ip address to the hosts which connected to the switch?

But when i just set ip address to the two hosts, and i found there are the two hosts mac address in switch! Is this the expected result? I even didn't ping between the two hosts, how the switch ...
YLearn's user avatar
  • 27.4k
5 votes
Accepted

Carrying remote VLAN via 2 routers to the local gateway

You can use Ether in IP, defined in RFC 3398 to tunnel ethernet through IP, if you equipment supports it. It's similar to the VxLAN approach, but a little simpler and older. If you don't have those ...
jonathanjo's user avatar
  • 16.3k
5 votes

GNS3 Routers - what is the difference beteween line con 0, line aux 0, and line vty 0 4?

Since GNS3 is a replication of the Cisco IOS, the difference is as followed: line con 0 This is the physical console port on the switch/router in which you can configure/troubleshoot the device. line ...
Cow's user avatar
  • 1,732
4 votes
Accepted

Is "Host unreachable" the same as "Communication administratively prohibited" in Access List ping response?

Practically it's the same. The router isn't silently dropping the packets but returning an ICMP error message 3/13, informing the sender that the packet has been filtered. Users often don't care why ...
Zac67's user avatar
  • 84.8k
4 votes

Duplex mismatch between a Fast Ethernet router and Gigabit Ethernet switch with auto negotiation

The message is from CDP duplex mismatch detection - it might indicate a duplex mismatch that isn't there, indicating a problem with CDP itself (esp. in GNS3). Check each side's interface status (show ...
Zac67's user avatar
  • 84.8k
4 votes

Difference between various network simulators

There's a fundamental distinction to make first, between a simulator and an emulator. A simulator is a program that replicate the behavior of the simulated device . It is as faithful to the original ...
JFL's user avatar
  • 19.7k
4 votes
Accepted

BGP (RIB-Failure - Higher admin distance)

The rib-failure is telling you the learned BGP route isn't best because there is another route -- in this case, directly connected routes -- with a better Admin Distance (AD). On R1 & R3 there is ...
Jeff Wheeler's user avatar
  • 5,468
3 votes
Accepted

Simulate a real L3 WAN with VIRL or GNS3 (+/- VIRL images)

You can simulate the L2 or L3 WAN, but only when it is functioning correctly. You won't be able to effectively simulate problems like signal fade, or unidirectional links. GNS3 and VIRL (and now EVE)...
Ron Trunk's user avatar
  • 67.6k
3 votes

BGP problems, cannot ping

You have not set the clock rate on the DCE side of the connection. The command is clock rate <rate>. See Cisco IOS Interface and Hardware Component Command Reference. Another problem is that ...
Ron Maupin's user avatar
  • 99.8k
3 votes

Configuring OSPF on two directly connected routers which are in different areas

To exchange routes in this topology you don't need two areas. A two-router setup would be best configured in a single area. Best practice is to configure them both in area 0, but if it's going to ...
Nathan L.'s user avatar
3 votes
Accepted

Virtual devices on GNS3 cannot ping the physical host

Since you can ping PC-1 from the physical PC (PH) but not vice versa, the most logical explanation is that PH doesn't reply to echo requests (firewall, filtering, ...). Edit after your added PH's ...
Zac67's user avatar
  • 84.8k
3 votes

Carrying remote VLAN via 2 routers to the local gateway

You can use VxLAN, defined in RFC7348, to span a VLAN onto different sites. Basically it encapsulates a VLAN into IP. This off course add some overhead, and your routers at each endpoint need to ...
JFL's user avatar
  • 19.7k
3 votes
Accepted

If traceroute fails why does ping still work?

That is because ping uses ICMP Echo Request and ICMP Echo Reply. Your traceroute is using UDP, which uses addresses called ports. Apparently, the port you are using in the traceroute commend is closed ...
Ron Maupin's user avatar
  • 99.8k
3 votes
Accepted

ipv6: I can ping only 1 interface within same network even with static route

You need to remember that ping is bidirectional. You send out an ICMP echo request, and you hope to get back an ICMP echo reply. That means that the replying device must also have a route back to the ...
Ron Maupin's user avatar
  • 99.8k
3 votes
Accepted

Juniper vMX Routers can't ping each other in GNS3

I think the interfaces you have connected in GNS3, em2 ---- em2 are actually named ge-0/0/0 by the vMX nodes. Try edit interfaces rename ge-0/0/2 to ge-0/0/0 on both vMX, commit, and check for ...
Jeff Wheeler's user avatar
  • 5,468
3 votes
Accepted

Unable to add an abbreviated IPv6 to a Cisco router

You are trying to configure a link-local address without the link-local keyword. ipv6 address fe80::1 link-local
Ron Maupin's user avatar
  • 99.8k
3 votes

GNS3 Router Telnet Configuration

You have to distinguish between the simulated network and the control of the simulator. The router is part of the simulation -- its networks are also part of the simulation. In real life, the console ...
Ron Trunk's user avatar
  • 67.6k
2 votes
Accepted

Is there no "mode on" for channel-group in GNS3?

The problem was existing because I was not using ether switch module ports that is added to router to handle it as switch
Ahmad Z. Tibi's user avatar
2 votes
Accepted

How to enable DHCP Cisco router

Move to configuration mode by typing this (you exclude address that you don't want the DHCP to assign to any device, e.g. printers, static IP addresses, etc.): Router# config t Router(conf)# ip dhcp ...
LD2's user avatar
  • 36
2 votes

Block ICMP ping from a PC to a PC

First you must deny the packets from host 3 to host 1; then permit any thing else. access-list 101 deny ip host 192.168.1.51 host 192.168.1.34 access-list 101 permit ip any any however, if you want ...
Devandroid's user avatar
2 votes
Accepted

How to assign multiple VLANS to a port?

I think you're assigning ports the wrong way. You have to specify each port before you enter the vlan command. Something like this: MainSwitch(config)#interface fastEthernet 1/4 MainSwitch(config-...
Ron Trunk's user avatar
  • 67.6k
2 votes

Should a PC populate its ARP table when a frame is not destined to it?

ARP replies are unicast, so the switch doesn't forward it to PC 3. Gratuitous ARPs are broadcast so all nodes can hear it.
Ron Trunk's user avatar
  • 67.6k
2 votes

How to connect two Juniper gns3 with fastethernet?

The em interfaces are the only usable interfaces on an Olive (Junos emulator). Although Junos will let you configure other interfaces, they will not show up, nor will the prefixes you assign to them ...
tonton gerrit's user avatar
2 votes
Accepted

GNS3 v2 router to host connection

I've noticed this for quite awhile with GNS3. I imagine that while you can see the ARP's via wireshark on the host, the host isn't actually receiving them. They're being sent out the host interface as ...
boomi's user avatar
  • 993
2 votes

GNS3 - Cisco router doesn't forward packets to different subnets

Your configuration on Router looks fine. It is likely the IP address configuration issue at Server_TFTP end. You need to verify the following things: IP address setting on Server_TFTP: IP address: ...
Hung Tran's user avatar
  • 3,754

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