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Add a limitations section to the HLD.
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‎L2/DHCP_Snooping/DHCP_Snooping_HLD.md

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- [5 Serviceability and Debug](#5-serviceability-and-debug)
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- [6 Warm Boot Support](#6-warm-boot-support)
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- [7 Scalability](#7-scalability)
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- [8 Unit Test](#8-unit-test)
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- [9 Internal Design Information](#9internal-design-information)
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- [8 Future enhancement](#7-future-enhancement)
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- [9 Unit Test](#9-unit-test)
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- [10 Internal Design Information](#10internal-design-information)
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# List of Tables
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[Table 1: Abbreviations](#table-1-abbreviations)
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# Revision
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| Rev | Date | Author | Change Description |
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|-----|-------------|--------------------|-----------------------------------|
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| 0.1 | 02/22/2021 | Phanindra TV | Initial version |
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| 0.2 | 03/31/2021 | Ravi Vemuri | More details added |
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| 0.3 | 06/07/2021 | Ravi Vemuri | Address review comments. |
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| Rev | Date | Author | Change Description |
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|-----|-------------|--------------------|------------------------------------------------------|
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| 0.1 | 02/22/2021 | Phanindra TV | Initial version |
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| 0.2 | 03/31/2021 | Ravi Vemuri | More details added |
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| 0.3 | 06/07/2021 | Ravi Vemuri | Address review comments. |
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| 0.4 | 07/15/2021 | Ravi Vemuri | Add Limitations/Future enhancements section |
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# About this Manual
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This document provides general information about the support for DHCPv4 snooping and DHCPv6 snooping in SONiC.
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;Stores user configured static DHCP bindings
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;Status: work in progress
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key = DHCP_SNOOPING_STATIC_BINDING|GLOBAL ; Global DHCP snooping static binding table key
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mac = mac-address ; client hardware address
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vlan = vlan-id ; DHCP snooping enabled vlan
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intf = interface ; front panel physical port or port channel
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ipaddress = ipv4 address / ipv6 address ; ipv4/ipv6 address
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key = DHCP_SNOOPING_STATIC_BINDING|mac|ipType ; DHCP snooping static binding table key - mac + "ipv4" or "ipv6"
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mac = mac-address ; client hardware address
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vlan = vlan-id ; DHCP snooping enabled vlan
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intf = interface ; front panel physical port or port channel
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ipaddress = ipv4 address / ipv6 address ; ipv4/ipv6 address
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#### 3.2.1.4 Trust Configuration
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;Stores dynamic DHCP bindings
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;Status: work in progress
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key = DHCP_SNOOPING_BINDING|GLOBAL ; Global DHCP snooping binding table key
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mac = mac-address ; client hardware address
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vlan = vlan-id ; DHCP snooping enabled vlan
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intf = interface ; front panel physical port or port channel
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ipaddress = ipv4 address / ipv6 address ; ipv4/ipv6 address
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lease_time = time in seconds ; time allotted by DHCP server, NA for static entry
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type = "static"/"dynamic" ; static or dynamic
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key = DHCP_SNOOPING_BINDING|mac|ipType ; DHCP snooping binding table key - mac + "ipv4" or "ipv6"
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mac = mac-address ; client hardware address
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vlan = vlan-id ; DHCP snooping enabled vlan
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intf = interface ; front panel physical port or port channel
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ipaddress = ipv4 address / ipv6 address ; ipv4/ipv6 address
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lease_time = time in seconds ; time allotted by DHCP server, NA for static entry
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type = "static"/"dynamic/tentative" ; static, dynamic or tentative
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### 3.2.3 Counters DB
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The following counters will be added to capture statistics. This section is TBD.
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Error receiving from DHCP snooping socket
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DHCP message too big
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Error sending from DHCP snooping socket
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Illegal source IP address in snooped packet
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Number of DHCP messages intercepted
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Number of DHCP messages processed
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Number of DHCP messages filtered
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Number of DHCP messages forwarded
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Number of DHCP message tx failures
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Rx REL or DECL from client not in bindings db
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Number of bindings added to bindings table
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Number of bindings removed from bindings table
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Number of DHCP messages dropped as static binding exists
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Packets discarded on unsupported outgoing interface
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Packets dropped due to no outgoing interface
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Error receiving from DHCP snooping socket
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DHCP message too big
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Error sending from DHCP snooping socket
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Illegal source IP address in snooped packet
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Illegal source MAC in snooped packet
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Number of DHCP messages intercepted
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Number of DHCP messages processed
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Number of DHCP messages filtered
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Number of DHCP messages forwarded
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Number of DHCP message tx failures
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Rx REL or DECL from client not in bindings db
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Number of bindings added to bindings table
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Number of bindings removed from bindings table
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Number of DHCP messages dropped as static binding exists
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Packets discarded on unsupported outgoing interface
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Packets dropped due to no outgoing interface
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## 3.3 COPP
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To bind a static IPv4 address to a Layer 2 interface
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sonic(config)#[no] ip source binding *IP-address* *MAC-address* vlan *vlan-id* {interface <interface name>}
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To clear all IP DHCP Snooping binding entries
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To clear all dynamic IP DHCP Snooping binding entries
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sonic(config)# clear ip dhcp snooping binding
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To clear a specific IP DHCP Snooping binding entry
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To clear a specific dynamic IP DHCP Snooping binding entry
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sonic(config)# clear ip dhcp snooping binding *IP-address* *MAC-address* vlan *vlan-id* {interface <interface name>}
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To bind a static IPv6 address to a Layer 2 interface
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sonic(config)#[no] ipv6 source binding *IP-address* *MAC-address* vlan *vlan-id* {interface <interface name>}
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To clear all IPv6 DHCP Snooping binding entries
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To clear all dynamic IPv6 DHCP Snooping binding entries
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sonic(config)# clear ipv6 dhcp snooping binding
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To clear a specific IPv6 DHCP Snooping binding entry
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To clear a specific dynamic IPv6 DHCP Snooping binding entry
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sonic(config)# clear ipv6 dhcp snooping binding *IP-address* *MAC-address* vlan *vlan-id* {interface <interface name>}
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##### 3.7.1.1.5 Configure an interface as trusted
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To display DHCPv6 Snooping statistics
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sonic# show ipv6 dhcp snooping statistics
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DHCP Snooping statistics can be cleared with the following commands
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sonic# clear ip dhcp snooping statistics
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sonic# clear ipv6 dhcp snooping statistics
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For example,
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console#show ip dhcp snooping
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DHCP Snoopoing feature allows 1024 Static entries to be configured. A total of 8K clients are supported (4K for DHCPv4 and 4K for DHCPv6). Beyond the limit, the DHCP Snooping DB is not updated and the DHCP packets are dropped.
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Go back to [Beginning of the document](#dhcp-snooping).
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# 8 Unit Test
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##8.1 CLI Test cases
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# 8 Future Enhancements, Limitations
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1. DHCP Snooping is not supported for clients/servers connected to MCLAG. DHCP Snooping binding entries are not currently synced between the MCLAG peers and hence DHCP messages may not be filtered if ingress is on a peer on which the binding was not created.
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Go back to [Beginning of the document](#dhcp-snooping).
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# 9 Unit Test
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##9.1 CLI Test cases
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1. Verify CLI to enable DHCPv4 Snooping globally
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2. Verify CLI to enable DHCPv4 Snooping per VLAN
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30. Verify CLI to enable debug logs for DHCP Snooping
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31. Verify CLI to enable DHCP Snooping debug logs per VLAN
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32. Verify CLI to enable DHCP Snooping debug logs per interface
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33. Verify CLI to configure trust mode for a range of interfaces, for DHCP4
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34. Verify CLI to configure trust mode for a range of interfaces, for DHCP6
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##8.2 Functionality test cases
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##9.2 Functionality test cases
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1. Verify that DHCP functionality is not impacted if DHCP Snooping is not enabled globally.
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2. Verify that once DHCP Snooping functionality is enabled globally, the DHCP messages received in VLANs that are not enabled for snooping are discarded.
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29. Verify that the VLAN on which DHCP snooping is enabled, cannot be deleted.
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30. Verify that trust/untrust configuration on a port is retained after a port shut/no-shut operation.
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31. Verify that a port can be set to 'trust' only if the VLAN to which it belongs has DHCP snooping enabled.
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32. Verify that DHCP Snooping dynamic binding entries are retained across warm boot
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33. Verify that DHCP Snooping dynamic binding entries lease time is updated with the time taken for warm boot operation.
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34. Verify that DHCP Snooping dynamic binding entires whose lease expired during the warm boot operation do not appear after warm boot is complete.
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Go back to [Beginning of the document](#dhcp-snooping).
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# 9 Internal Design Information
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# 10 Internal Design Information
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![DHCP snooping high level architecture](ds_packet_flow.png)
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Go back to [Beginning of the document](#dhcp-snooping).

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