Ticket 14 – EIGRP Passive Interface

In regards to the following note: “Just for your information, in fact Clients 1 & 2 in this ticket CANNOT receive IP addresses from DHCP Server because DSW1 cannot reach 10.1.21.129 (an loopback interface on R4) because of the “passive-interface default” command. But in the exam you will see that Clients 1 & 2 can still get their IP addresses! It is a bug in the exam.”

THIS IS *NOT* A BUG. This case can happen in real life if the problem happened *after* the client got an IP address. Imagine the following case:

1. All working
2. Client gets IP address
3. Someone breaks the config so dhcp is not reachable anymore (which is the case in this ticket)
4. The client still has the IP address

This is a good simlet in the sense that simulates what could actually happen in the real world.

I see that at least PC1 has static ip assigned, so no need of DHCP server here

Guys,
Is the note important at the exam ? or is it just for the packet-tracer lab ?

Note: There is a loopback interface on this device which has an IP address of 10.1.21.129 so we have to include the “network 10.1.21.128 0.0.0.3” command.

@Henrico
10.1.21.129 is a loopback address means (directly connected network) on R4.. It is also an IP-Helper address on DSW-1. Even if you don’t advertise this in EIGRP process, the clients (PC-1 or PC-2) can still get IP from DHCP server (R4). Do you know why ?? If you have good concepts of networking, then you will understand this scenerio in a minute.

The clients can get DHCP IP from R4 without that network advertisement, because of the fact that “Default Route / Default Gateway” is installed on DSW-1 routing table which is EIGRP-EX route. This route will be installed after making EIGRP neighborship. So any request destined for 10.1.21.129 (even though this network is not visible in routing table, so it will be forwarded out through default route installed) will be forwarded out on R4’s interface.

So no need to add this command: “network 10.1.21.128 0.0.0.3” . But first check the DSW1’s routing table before closing this ticket.

@Majid,
first of all, i appreciate your response.
secondly, there is no default gateway installed in dsw1’s routing table.

I think the note points out the result of issuing “no passive interface”.

Hi All,

If R4 has no interfaces running EIGRP, then how is it that R3 has routes for the networks 10.2.0.0/16 as an N2 route? It means that those EIGRP routes were passed from DSW1 to R4 and redistributed into OSPF successfully.

Please explain.

EIGRP PASSIVE INTERFACE TICKET

Hi All,

If R4 has no interfaces running EIGRP, then how is it that R3 has routes for the networks 10.2.0.0/16 as an N2 route?

It means that those EIGRP routes were passed from DSW1 to R4 and redistributed into OSPF successfully.

Please explain.

failed today. this question got me really good. spent over 1h on it. there was no eigrp neighbor on r4, so the neighborship was not established. The problem is that “no passive interface” was not present in any of the choices for r4 (I checked all technologies too) Also, config already had this command on int to DSW. No idea what the right answer was.

Here is my approach:

1) First verify the problem exist => unsuccessful ping from Client 1 to web server.
2)Ping R4(10.1.4.5 or 6) – unsuccessful. Go to R4 and try to ping web server and it is successful. Try to ping client 1 from R4 = unsuccessful ===> Something might be going on around R4
3) Do pings from DSW2. Can ping Client 1 but cannot ping R1. Check routing table with sh ip route – there are no routes from R1 which is connected to the web server so something is stopping them from R4.
4)Head over to R4 and do a show run – we see there is a passive-interface default command applied which turns off the sending and receiving of OSPF packets on all interfaces on R4 hence the problem.

Solution we need to enable EIGRP in incoming interfaces on R4(fa0/0 and fa0/1) connecting to DSW1 and DSW2

Hi All, I have passed Tshoot exam today with 1000/1000. 13th-Nov-2019 MCQs questions, simlets and tickets are all valid! NO new questions or tickets. To narrow down issue I normally ping 209.65.200.241 from R1, then R2>>>R3>>>R4>>>DSW1>>>Client & do ipconfig on client ping client IP 10.2.1.3 from DSW >>>R4 >>>R3 >>>R2>>>R1.

I had premium account, after spending 4 hours I booked exam. CCNP route is theory, CCNP TSHOOT is practical and very easy.

Thank you for Networktut for all hard work, this website truly help me to achieve full score (1000)
I like to share my experience, which may be helpful for you to pass the exam
MCQs seen from Nov, but make sure read questions carefully as they are coming with detailed scenarios
To disable passive interface only option appears in the exam as no ip passive-interface eigrp 10 under interface configuration mode. So we have to choose it.
As per my experience this command is not working on all Cisco versions. Cisco 7200 series doesn’t support for this command, which I used in GNS3
No 13 appears with incorrect DHCP helper address
It was quite tricky
Client1-> ipconfig shows with 169.— so decided to go through bottom-up approach
ASW1->show ip interface brief f1/0/0 and f1/0/2 connected to Clients show up with up/up status.
However when I applied show port-security given the out put with violation count 1 and status shutdown per each interface. quite confused..I didn’t choose remove port-security option.so rather choosing port security issue I decided to investigate further.
So found incorrect IP helper-address 10.2.21.129(which doesn’t exist in routing table and no such IP available in DHCP router)
So therefore I decided to choose correct IP helper address 10.1.21.129
So please don’t blindly choose answers

Pls. pls. carefully check configuration,

Wishing everyone Good-Luck

@Klimy ““Client 1 can’t ping R4” ? Why ? DSW1 is directly connected to R4. I don’t see why would you need any IGP for the PING to work. You mean the loopback of R4 ?
What’s in the real ticket ?”

Fully agree with Klimy. This confused me really badly. The 10.1.4.4/30 is directly connected and from the PC1 i can ping the DSW1. Following the logic, PC1 should be able to ping R4… ARP Table is also ok… This lead me to the false trail and I spend 15 Minutes searching what is wrong…

Any clue?

Novost