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BigIron RX Series Configuration Guide
53-1002253-01
Protecting against Smurf attacks
34
Avoiding being an intermediary in a Smurf attack
A Smurf attack relies on the intermediary to broadcast ICMP echo request packets to hosts on a
target subnet. When the ICMP echo request packet arrives at the target subnet, it is converted to a
Layer 2 broadcast and sent to the connected hosts. This conversion takes place only when
directed broadcast forwarding is enabled on the device.
To avoid being an intermediary in a Smurf attack, make sure forwarding of directed broadcasts is
disabled on the device. Directed broadcast forwarding is disabled by default. To disable directed
broadcast forwarding, do the following.
BigIron RX(config)# no ip directed-broadcast
Syntax: [no] ip directed-broadcast
ACL-based DOS-attack prevention
ACL-based DOS-attack prevention provides great flexibility on what packets can be rate-limited or
dropped up. In fact, users can create any matching conditions they want to regulate any particular
traffic flow they have in mind. This section provides examples that can be used to prevent two
common types of DOS attacks.
Avoiding being a victim in a Smurf attack
You can configure the device to drop ICMP packets when excessive numbers are encountered, as is
the case when the device is the victim of a Smurf attack. You can set threshold values for ICMP
packets that are targeted at the router itself or passing through an interface, and drop them when
the thresholds are exceeded.
For example, to set threshold values for ICMP packets received on interface 3/11, enter the
following command.
BigIron RX(config)# access-list 101 permit icmp any any echo-reply
BigIron RX(config)# int e 3/11
BigIron RX(config-if-e100-3/11)# dos-attack-prevent 101 burst-normal 5000000
burst-max 1000 lockup 300
In the example, if the total traffic volume of ICMP echo-reply packets received per second exceeds
5,000,000 bits per second, the excess packets are dropped. If the number of ICMP echo-reply
packets received per second exceeds 1,000, the device drops all ICMP packets for the next 300
seconds (five minutes).
Syntax: dos-attack-prevent <
num
> burst-normal <
bps
> burst-max <
num-of-packets
> lockup
<
seconds
> [log]
<
num
> is the ACL ID that will be used to check for traffic conformance.
The parameters burst-normal, burst-max, and lockup are applied individually on each ACL filter.
The burst-normal value, 1 – 100000000, is specified as bits per second.
The burst-max value, 1 – 100000, is specified as number of packets.
The lockup value can be from 1 – 10000 seconds.
The number of incoming ICMP packets that match the condition specified in the ACL per second
are measured and compared to the threshold values as follows:
Содержание BigIron RX Series
Страница 100: ...24 BigIron RX Series Configuration Guide 53 1002253 01 Logging on through the Web Management Interface 2 ...
Страница 192: ...116 BigIron RX Series Configuration Guide 53 1002253 01 Configuring authentication method lists 4 ...
Страница 228: ...152 BigIron RX Series Configuration Guide 53 1002253 01 Enabling WAN PHY mode support 6 ...
Страница 312: ...236 BigIron RX Series Configuration Guide 53 1002253 01 Displaying IP information 7 ...
Страница 356: ...280 BigIron RX Series Configuration Guide 53 1002253 01 Resetting LLDP statistics 9 ...
Страница 402: ...326 BigIron RX Series Configuration Guide 53 1002253 01 Transparent firewall mode 11 ...
Страница 432: ...356 BigIron RX Series Configuration Guide 53 1002253 01 SuperSpan 12 ...
Страница 500: ...424 BigIron RX Series Configuration Guide 53 1002253 01 MRP CLI example 14 ...
Страница 580: ...504 BigIron RX Series Configuration Guide 53 1002253 01 Configuring multicast traffic engineering 18 ...
Страница 591: ...BigIron RX Series Configuration Guide 515 53 1002253 01 Displaying traffic reduction 19 ...
Страница 592: ...516 BigIron RX Series Configuration Guide 53 1002253 01 Displaying traffic reduction 19 ...
Страница 598: ...522 BigIron RX Series Configuration Guide 53 1002253 01 Viewing Layer 2 ACLs 20 ...
Страница 656: ...580 BigIron RX Series Configuration Guide 53 1002253 01 Trunk formation 22 ...
Страница 754: ...678 BigIron RX Series Configuration Guide 53 1002253 01 Displaying RIP filters 24 ...
Страница 814: ...738 BigIron RX Series Configuration Guide 53 1002253 01 Displaying OSPF information 25 ...
Страница 932: ...856 BigIron RX Series Configuration Guide 53 1002253 01 Generalized TTL security mechanism support 26 ...
Страница 980: ...904 BigIron RX Series Configuration Guide 53 1002253 01 Clearing IS IS information 28 ...
Страница 1000: ...924 BigIron RX Series Configuration Guide 53 1002253 01 Using secure copy 30 ...
Страница 1088: ...1012 BigIron RX Series Configuration Guide 53 1002253 01 IP source guard 35 ...
Страница 1108: ...1032 BigIron RX Series Configuration Guide 53 1002253 01 Reading CDP packets 37 ...
Страница 1126: ...1050 BigIron RX Series Configuration Guide 53 1002253 01 Clearing sFlow statistics 39 ...
Страница 1140: ...1064 BigIron RX Series Configuration Guide 53 1002253 01 802 1s Multiple Spanning Tree Protocol 40 ...
Страница 1324: ...1248 BigIron RX Series Configuration Guide 53 1002253 01 Displaying OSPFv3 information 48 ...
Страница 1363: ...BigIron RX Series Configuration Guide 1287 53 1002253 01 Continuous System Monitor 51 ...
Страница 1364: ...1288 BigIron RX Series Configuration Guide 53 1002253 01 Continuous System Monitor 51 ...
Страница 1404: ...1328 BigIron RX Series Configuration Guide 53 1002253 01 Commands That Require a Reload D ...
Страница 1458: ...1382 BigIron RX Series Configuration Guide 53 1002253 01 VSRP E ...