9 votes
Accepted

Different Behaviour of a Router

You don't have to add anything in the 1st case because it's automatic. As there's only one router, it obviously knows everything directly connected to it. When that becomes more than one router, some ...
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  • 29.5k
9 votes

Different Behaviour of a Router

Why in the first case, There was no need of adding Routing table Because it's not really true that there was no need of adding a routing table. When you configured the IP addresses and subnets of the ...
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  • 191
7 votes
Accepted

Layer 3 Switching in Packet Tracer not working

On the switch, your IP for interface vlan 20 is wrong. # interface vlan 20 # ip address 10.1.2.1 255.255.255.0 # no shutdown Then make sure you have ip routing on. Also the gateway for PC A should ...
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7 votes
Accepted

What's the difference between Serial DCE and Serial DTE link?

One side of the link (DCE), has to transmit the clock signal, which controls the data rate, and the other side (DTE) receives the clock signal. R1 is DCE here: interface Serial0/0/0 ip address 10.0....
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  • 15.9k
7 votes

missing Packet tracer physical Tab

Try select Option from menu bar, click "Preference", switch to "Hide" tab and uncheck the "Hide physical tab" box. Hope this helps.
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6 votes
Accepted

Whats's the function of a loopback interface in routing protocols?

The loopback interface is useful because it is an interface with an IP address which never goes down. OSPF, without a specifically defined Router ID, will pick a Router ID on its own. It chooses the ...
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  • 92.9k
6 votes
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Why can't I ping in this situation?

You have the 10.0.0.0/8 and 172.16.0.0/16 networks defined on both the middle and right routers. Using auto-summary on both makes each think they own those whole summarized networks, so they will not ...
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  • 92.9k
6 votes

Why can't two hosts (in two different logical networks) connected to each other through cross-over cable communicate?

A host knows if the destination address is on a different network (the same way that you do, by masking the host and destination addresses with the host mask). If the destination is on the same ...
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  • 92.9k
6 votes

Why aren't mac addresses of a serial port shown on packet tracer

Serial ports don't have or need MAC addresses. It's as simple as that.
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6 votes
Accepted

delete object network in cisco ASA with packet tracert

It's giving you that/those error(s) because removing that object would leave the access-list empty but still existing, which is not possible or allowed, and you can't delete an access-list like that (...
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  • 4,436
5 votes

Dual Stack Network Configuration

Dual stack means that an interface can communicate with both v4 and v6 clients. It DOES NOT mean that it will translate between the two. For that, you need to implement NAT-PT, to translate between ...
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  • 62k
5 votes

All OSPF routes lost when interface fails

The message you got is perfectly normal. That is not OSPF crashing, but it is telling you that the neighbor is no longer there. The interface is down, so OSPF cannot communicate with that neighbor. ...
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  • 92.9k
5 votes
Accepted

OSPF - Default route doesn't get advertised to all areas

1. The first issue is that you configured same Router-ID (RID) router-id 1.1.1.1 for R1 and R2 in area 45. All OSPF router should have different RIDs across the OSPF network domain. 2. And the ...
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  • 3,744
5 votes
Accepted

Multiple access lists on same vlan

You can't have more than one access list per direction on an interface. So, to accomplish this, you will have to create a unique access-list for each interface that allows only the traffic you want.
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  • 62k
5 votes
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Show interfaces brief information

The most common commands are show interfaces show ip interface brief Or for a specific interface show interfaces vlan 1
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  • 15.9k
5 votes
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What is wrong with this set of routers?

R2's default route points back to R1. Instead it needs to point to R3 via Serial0/0/1.
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  • 69.5k
5 votes

i cant configure the ip adress and subnetmask ,i only have one router "1941" and 2 pc's

You misspelled "address". Using the tab-completion feature on most devices usually helps with spelling errors :)
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  • 95
5 votes

Why aren't mac addresses of a serial port shown on packet tracer

MAC Addresses are specific to Ethernet interfaces - serial interfaces are point-to-point and use a different Layer 2 protocol (PPP, HDLC, FR etc.) for communication. EUI-64 is most likely deriving it'...
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5 votes
Accepted

Default gateway of host connected to two routers via switch

Because you have not a star-shaped network, you have to define a route to reach each network. Your routes can be : 192.168.2.0/24 via 192.168.1.254 Default via 192.168.1.253 or 192.168.2.0/24 via ...
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  • 166
5 votes
Accepted

inconsistent bad mask error

The mask you were trying to use really is a bad mask. You were trying to use 255.255.225.248. You simply had a typographical error that you eventually corrected. It happens, and it is a big reason ...
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  • 92.9k
4 votes

Dual Stack Network Configuration

In a dual stack network, a host has both an IPv4 and an IPv6 configuration allowing them to choose which protocol to use. When communicating with an IPv6 host, it will use its IPv6 address, when ...
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  • 4,601
4 votes

Whats's the function of a loopback interface in routing protocols?

First, loopbacks interfaces are mainly used when we want to establish adjacencies between 2 equipments (i.e. routers) and to be sure that when one link fails, the adjacency will not go down because, ...
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4 votes
Accepted

Will STP portfast prevent a loop?

Port fast bypasses the usual STP phases and goes straight into forwarding. This is useful for ports connected to end-devices which use DHCP. It does not stop BPDUs, and there are those who advocate ...
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  • 92.9k
4 votes

Calculated window size in Wireshark

This post has a good explanation for what you're seeing. What you see is normal behavior. Both sides send a small window size and neither announce that they are able to use window scaling. So in ...
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  • 2,317
4 votes
Accepted

OSPF cannot communicate inter-area

You don't have an Area 0. Areas can only talk to Area 0. This is an OSPF basic feature which helps prevent routing loops. Router 1 needs to be in Area 0. Try something like this: Router0: ...
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  • 92.9k
4 votes
Accepted

How to sniff a switched LAN by plugging the laptop into a switch port

The easy part: Use Wireshark for the sniffing. The hard part: In a switched network you need support from the switch to get all the traffic. It is called "port mirroring", "span port", "monitor port" ...
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4 votes

DHCP Server giving the wrong IP address and DHCP server failed Apipa being used

It appears that some of your ports are in VLANs that do not have ip helper addresses on the router. They won't get addresses from your server.
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