🎆Networks Security

On Cisco Equipments.

Cam OverFlow - Protection

The actual way to prevent a CAM table overflow attack is to instruct each port that there's a limit to how many MAC addresses it can have, and that's done with port security.

On Switches :

S1#configure terminal
S1(config)#int range f0/1 - 24
S1(config-if)#no shut
S1(config-if)#switchport mode access
S1(config-if)#switchport port-security maximum 5
S1(config-if)#switchport port-security
S1(config-if)#do show port-security
exit

If an attack occurs, on the switch do :

show port-security
show inter status err-disabled

DHCP Starvation - Protection

Protection

Limit rate on every interfaces :

Results :

Wireshark

DHCP Transactions

CDP Flooding - Protection

On Switches :

S1(config-if)# no cdp run
S1# sh cdp interface int
S1# show cdp neighbors

Disable on all ports except the one connected to R1.

Why did Cisco create CDP ?

Cisco Discovery Protocol (CDP) is a Cisco proprietary protocol designed to facilitate the network management of Cisco devices by discovering hardware and protocol information about neighboring devices. By using CDP, Network Engineers can gather information about neighboring network devices, determining the type of hardware or equipment, software version, active interfaces the device is using (whether physical or VLAN), how they are configured, and other useful information. That is quite a bit of information, and this is useful for troubleshooting and documenting the network.

TCP Syn Flood - Protection

Articles | Cisco Presswww.ciscopress.com

Security Configuration Guide: Denial of Service Attack Prevention, Cisco IOS Release 15M&T - Configuring TCP Intercept (Preventing Denial-of-Service Attacks) [Support]Cisco

TCP Intercept

Steps on the switch

enable
configure terminal
access-list access-list-number {deny | permit | remark} {host-ip-address | any | host}
ip tcp intercept list access-list-number
ip tcp intercept mode {intercept | watch}
ip tcp intercept drop-mode {oldest | random}
ip tcp intercept watch-timeout seconds
ip tcp intercept finrst-timeout seconds
ip tcp intercept connection-timeout seconds
ip tcp intercept max-incomplete low number high number
ip tcp intercept one-minute low number high number
exit
show tcp intercept connections
show tcp intercept statistics

OSPF - Protection

On routers, setting up authentication process :

R1(config)# router ospf 1
R1(config-router)# area 0 authentication message-digest
R1(config-router)# exit
R1(config)# int g1/0
R1(config-if)# ip ospf message-digest-key 1 md5 passworD
R1(config-if)# int s0/1/1
R1(config-if)# ip ospf message-digest-key 1 md5 passworD

During the attack :

ARP Spoofing - Protection

On Switches : DHCP snooping & rate limit.

VLAN Hopping - Protection

Verification

During an attack :