Questions tagged [security]

A general purpose tag to mark discussions of general security topics including firewalls, ACLs, AAA and numerous others related to keeping the network safe from unauthorized access.

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3answers
3k views

whois 243.25.203.20

I see this ip address actively accessing gmail account in spite of 2-Step Verification. whois 243.25.203.20 produces following message: No whois server is known for this kind of object. How can I ...
2
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0answers
31 views

Arp Protect in dynamic VLAN environment

I am using 802.1x authentication with dynamic Vlan assignment(CPPM). As you may know, when a user logges in to their computer, SW attaches the user port to related Vlan. Thinking the scenario in which ...
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2answers
2k views

Can you only allow local login when TACACS is unavailable on a Juniper?

I'm pretty sure you can do this in the Cisco world, but haven't found a way to do this on a Juniper device. Is there a way to restrict local accounts from being accessed if the router has access to ...
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2answers
140 views

Configuring a network for 100% isolation (for security)

I'm configuring a LAN for an office. It's a new setup, and therefore there are desktops but no servers and no PC-to-PC communications - everything is on the cloud. The exception to this are several ...
2
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2answers
411 views

Listen-only (stealth) CDP on IOS

I would like to put my router in a listen-only mode for CDP i.e. it should allow CDP packets to only arrive while not advertising so that I can glimpse into physical topology while remaining hidden to ...
4
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1answer
1k views

Cisco Catalyst 2960 X MAC access list

I am using a MAC access list on this switch, so I go about it by first creating the MAC access list: #conf t #mac access-list extended aclname # permit host XXXX.XXXX.XXXX any Then, I tie this list ...
1
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2answers
39 views

The Best Way to Secure sFlow Exports?

Hi Network Masters, I have recently gotten my network devices to export sFlow records to my sFlow collector. Trouble is, all those sFlow exports are being sent across my network in cleartext. A lot ...
1
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1answer
71 views

How to implement port security in SDN using pox controller and ovs?

How can I defend against DHCP starvation attacks or MAC spoofing in an SDN environment?
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3answers
64k views

How to verify that a UDP port is open? [closed]

I have here a dilemma. I have a device that communicates to another remote device but there is a firewall between them. It's a UDP connection, so TCP utilities don't work to test if the specific port ...
2
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1answer
74 views

What is the purpose of native VLAN on a trunk link?

Most VLAN articles I've read recommend avoid using VLAN1 for ports with untagged traffic (aka access ports). I've heard enough of this nonsense. Except for the reserved values of 0x000 and 0xFFF, a ...
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0answers
41 views

Compatible peap+freeradius+openldap

On my new job I have inherited a service wpa2-enterprice with peap+freeradius+openldap. As NAS we use ArubaIAP with enabled function "eap-termination". And this bundle works well! Little deep: In ...
0
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1answer
20 views

Are Port Numbers Strictly Attached to the Protocol? [duplicate]

I was playing around with hosting a local webserver, and decided to host it on port 53 as an experiment. Turns out I was able to make an HTTP GET request to localhost:53 without any issues (using ...
1
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1answer
113 views

Cisco ASA looping broadcast packet

I have small office where running cisco ASA ASA5506 and version 9.4(1) and it's also configured for IPsec VPN tunnel, My LAN subnet is 10.1.1.0/24 So i have found very interesting things in LAN ...
1
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2answers
65 views

Different Wi-Fi security levels under same private subnet

I'm working on an assignment and I'm given a hypothetical scenario where: A company has a local subnet where everything shares the flat address space 192.168.0.0/8 (this means that any device can ...
3
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1answer
75 views

Is TR-069 a security risk?

My ISP provides a combo box (ONT + router + switch + Wi-Fi) which they can manage remotely, likely using TR-069. They automatically push default configurations to the device. After I do a factory ...
6
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4answers
10k views

Toggle Switch for an Ethernet Cable

Is it possible to place a switch in one of the four/five wires of an Ethernet cable that will disable it? For my hardware project I would like the user to be able to disable the internet connection ...
2
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3answers
146 views

What's the advantage of having VLANs if you enable inter-vlan routing?

If you configure VLANs with each having their own subnets, is there a point to have them if inter-vlan routing is enabled? Since VLANs will have access to other VLANs, the security argument is not ...
0
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1answer
55 views

What is the difference between VPN and Domain fronting?

What is Domain fronting? and how it is different from a VPN?
5
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1answer
375 views

Hardening Cisco router on Internet-MANAGEMENT PLANE

I need confirmation that I understood the Cisco manual right. So my network is like this: ISP_RTR ---x.x.x.x/30--- Perimeter/Edge_RTR ---y.y.y.y/30--- FW1 --- DMZ1 ...
0
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1answer
18 views

Session, presentation and application layer

I almost finished the ccna, in the meantime I'm following Pentesting courses, I noticed enough interesting protocols at the session level. I wish I could understand them as I did with cisco, but I ...
0
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1answer
29 views

Is Network Bridging secure [closed]

Bridging two network cars in Windows allows the two separate networks to connect. Assuming there are three NIC cards present in a machine: A, B and C. If I bridge NIC A and B, is there a possibility ...
2
votes
1answer
391 views

Why does the Implicit Rule prevent traffic from passing?

I an testing traffic forwarding between different DMZ with different security levels. DMZ: interface GigabitEthernet0/1.351 vlan 351 nameif dmz security-level 10 ip address 10.100.20.1 255.255....
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1answer
54 views

Multicast in enterprise network

Once I have heard from a professional that multicast is forbidden (or not suggested or not allowed) in enterprise networks from 2014. (He referenced to a standard or recommendation document or ...
2
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2answers
781 views

How can we identify layer two device in a network or what are those device effects on a frame

This is sample of a traceroute to google.com: TraceRoute from Network-Tools.com to 216.58.194.46 [google.com] Hop (ms) (ms) (ms) IP Address Host name 1 0 0 0 ...
1
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1answer
45 views

Is this computer a threat? On same network range, but in a workgroup

We have a normal on-premise Class C network with an internal IP address scheme of 192.168.15.x (hypothetical). We have a SonicWALL device that acts as a VPN server for external clients, a DHCP server ...
1
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1answer
53 views

SDN Flow-modification attack

What are the steps that can be taken to prevent flow-modification attacks on an SDN controller? The attack would look as follows(As seen by the image): Does OpenDaylight or any other controller have ...
1
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1answer
165 views

Cisco ASA not passing traffic between two interface

I have Cisco 5506 with Security Plue License and following is my configuration. interface GigabitEthernet1/1 nameif inside security-level 100 ip address 10.0.10.1 255.255.255.0 ! interface ...
2
votes
1answer
120 views

Can I send an HTTP reply to users who try to access a blocked URL via the Cisco ASA?

A customer is requesting a way to send a customized reply to users who attempt to access invalid URLs via HTTP and get blocked by the ASA (v9.6). (We are currently using Regex filtering and Botnet ...
2
votes
1answer
91 views

MAC Address not resolving when IPSec VPN in place

I've created an IPSec VPN connection between two Mikrotik routers. They are connecting via IKEv2. Inside our two networks, we have a printer spooler which needs the printer's MAC address to verify it'...
0
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1answer
59 views

How to change ip TTL=1 on flat network for security [closed]

Working on a network at an high rise apartment complex. They have a core router/firewall acting as dhcp server and about 7 switches (all l3 switches). They have a few vlans to segment traffic based of ...
4
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2answers
523 views

why do we use a layer 2 switch in a DMZ rather than a layer 3?

I've been trying to learn about DMZs. It's hard to find a technical explanation that does not dive head long into the complexities of Cisco hardware, which I'm finding confusing as I'm new to ...
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1answer
228 views

IPSec SA being Unidirectional

From what I’ve read, IKE SAs are Birectional and IPSec SAs are unidirectional. But if the same proposals are to be agreed by both the ends, say protocol esp, Authentication algorithm as hmac-sha1-...
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1answer
50 views

Why aren't we using digital signatures for the DHCP?

Why aren't we using digital signatures for the DHCP in order to stop Rouge DHCP attacks?
1
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1answer
50 views

Protect Cisco C3560CX switch from unauthorized access on remote location

I have to extend our corporate lan to remote location on which we can not control the physical access to the switch. What are the best practices in this case/scenario? So, I will shut down password ...
3
votes
1answer
45 views

Why aren't we encrypting data on Network level instead of transport level when using e.g. HTTP [closed]

Why we are bothering to encrypt our data on a transport level, instead of just doing that on a network level with e.g. IPSec and get rid of the need to to that in upper layers. For example instead of ...
4
votes
1answer
383 views

Lost Ethertype in encrypted MACsec frames

MACsec uses an Ethertype of 88E5. This presents an obvious problem when encrypting frames which already have, or should have, another Ethertype. This RedHat blog, for example, states "[MACsec] can ...
3
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1answer
298 views

Must a broadcast request come from the same network?

I was reading about Smurf Attacks and how Smurf Amplifier Registry keeps track of servers used for amplifying the attack, then I wondered, can a request coming from anywhere broadcast it to all parts ...
1
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3answers
2k views

BGP community blackhole

We have created peer with our ISP and my ISP send community to do backhole but how do i configure that and send community string for blackhole traffic. ISP said use 64682:0 community for RTBH, I did ...
4
votes
1answer
829 views

IPv6 BGP peering via link-local addresses

I'm planning to run BGP with my upstream provider and advertise our global IPv6 prefixes. I'd like to use only link-local addresses between the ISP's router and my border router to make the border ...
4
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5answers
1k views

Are there any security advantages to activating VLAN tagging?

I understand the concepts of generating a VLAN. However, on a small, closed, sophisticated network, are there any security advantages to activating VLAN tagging?
4
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3answers
721 views

What practices/ mechanisms/ protocols can be used to secure communication on physically exposed Ethernet links?

Given that Ethernet cables are everywhere and use for all kinds of links and it is assumed they are physically guarded, hence typical installations do not leverage any "secure" mechanisms. Let's say ...
1
vote
2answers
58 views

Unidirectional Subnet Communication

Let me first begin by saying I've looked around, and I haven't found a question asked that pertains to this situation exactly. Essentially my question is this: Is it possible to allow subnet S1to ...
2
votes
1answer
208 views

How does Sourcefire IPS understand which application is sending the packet?

I wanted to understand how does the Sourcefire NGIPS understand which application has initiated the traffic. I am aware that the protocol is learned from the ports, but, how does it determine that so ...
1
vote
1answer
99 views

Unsecured devices and IPv6

I'm currently starting to read up on IPv6, and as soon as I heared that every device can/will have a public accessible adreess i got a little freaked out. There are a lot of horror stories about ...
2
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2answers
2k views

ASA not allowing ping to distinct interface IP

I have following scenario where i am trying to ping from 10.30.1.100 PC to ASA interface 10.20.1.1 not pinging but i can ping 10.20.1.100 so why ASA not allowing to ping distinct interface but ...
1
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1answer
42 views

Network Security Tunnel

In the Tunnel Interface, when I edit the tunnel information, it shows: Attributes Values Tunnel Source IF10 Tunnel Destination 1.0.0.1 Tunnel Mode GRE What does IF10 ...
1
vote
1answer
2k views

How does a Cisco ACL handle fragments

We have an ASR1000, and I have the following ACL, but yesterday someone hit us with big DDoS attack, and I found it was a DNS amplification attack. so all source port for 53, and it was definitely a ...
3
votes
1answer
1k views

Locked myself out of my Cisco switch

I have officially made the dumbest mistake ever. My switch is a Catalyst 2960 Series, configured this way: Current configuration : 10052 bytes ! ! Last configuration change at 19:15:28 UTC Wed Oct ...
1
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3answers
2k views

Unknown Unicast Flooding

I'm focusing currently on the "Unknown Unicast Flooding", and the proposed solutions from Cisco. I really need deep information about: Cisco Blocking Unknown Unicast Flooding (UUFB) Unknown Unicast ...
3
votes
1answer
769 views

ACL on trunk Port

our network infrastructure as showing the image below I had to give an external company (dealing with Face recognition) software an access to both the server (172.26.33.56) and the IP Camera (172.26....

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